[MLIR][spirv] Fix links in docs after repo migration

[antiagainst]

Summary

This commit updates links to SPIR-V dialect code to LLVM monorepo
on GitHub. It also points to the operation doc on mlir.llvm.org.

[merge_guards_bot]

Unit tests: pass. 61128 tests passed, 0 failed and 728 were skipped.

clang-tidy: pass.

clang-format: pass.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

[mehdi_amini]

mlir/docs/Dialects/SPIR-V.md

1020

This should point to https://mlir.llvm.org

(but this entire document should be generated)

[antiagainst]

mlir/docs/Dialects/SPIR-V.md

1020

Oh, right. Will update this later. Thanks for the good catch! :)

mlir/docs/Dialects/SPIR-V.md

 
 ```mlir
 %0 = "spv.constant"() { value = 42 : i32 } : () -> i32
 %1 = "spv.Variable"(%0) { storage_class = "Function" } : (i32) -> !spv.ptr<i32, Function>
 %2 = "spv.IAdd"(%0, %0) : (i32, i32) -> i32
 ```
 
 Operation documentation is written in each op's Op Definition Spec using
-TableGen. A markdown version of the doc can be generated using `mlir-tblgen
--gen-doc`.
+TableGen. A markdown version of the doc can be found at
+[mlir.llvm.org][LlvmMlirSpirvDoc] or generated using `mlir-tblgen -gen-doc`.
 
 ### Ops from extended instruction sets
 
 Analogically extended instruction set is a mechanism to import SPIR-V
 instructions within another namespace. [`GLSL.std.450`][GlslStd450] is an
 extended instruction set that provides common mathematical routines that should
 be supported. Instead of modeling `OpExtInstImport` as a separate op and use a
 single op to model `OpExtInst` for all extended instructions, we model each

 [SpirvGrammar]: https://raw.githubusercontent.com/KhronosGroup/SPIRV-Headers/master/include/spirv/unified1/spirv.core.grammar.json
 [GlslStd450]: https://www.khronos.org/registry/spir-v/specs/1.0/GLSL.std.450.html
 [ArrayType]: https://www.khronos.org/registry/spir-v/specs/unified1/SPIRV.html#OpTypeArray
 [ImageType]: https://www.khronos.org/registry/spir-v/specs/unified1/SPIRV.html#OpTypeImage
 [PointerType]: https://www.khronos.org/registry/spir-v/specs/unified1/SPIRV.html#OpTypePointer
 [RuntimeArrayType]: https://www.khronos.org/registry/spir-v/specs/unified1/SPIRV.html#OpTypeRuntimeArray
 [StructType]: https://www.khronos.org/registry/spir-v/specs/unified1/SPIRV.html#Structure
 [SpirvTools]: https://github.com/KhronosGroup/SPIRV-Tools
-[Rationale]: https://github.com/tensorflow/mlir/blob/master/g3doc/Rationale.md#block-arguments-vs-phi-nodes
-[ODS]: https://github.com/tensorflow/mlir/blob/master/g3doc/OpDefinitions.md
-[GreedyPatternRewriter]: https://github.com/tensorflow/mlir/blob/master/lib/Transforms/Utils/GreedyPatternRewriteDriver.cpp
+[Rationale]: https://github.com/llvm/llvm-project/blob/master/mlir/docs/Rationale.md#block-arguments-vs-phi-nodes
+[ODS]: https://github.com/llvm/llvm-project/blob/master/mlir/docs/OpDefinitions.md
+[GreedyPatternRewriter]: https://github.com/llvm/llvm-project/blob/master/mlir/lib/Transforms/Utils/GreedyPatternRewriteDriver.cpp
 [MlirSpirvHeaders]: https://github.com/tensorflow/mlir/tree/master/include/mlir/Dialect/SPIRV
 [MlirSpirvLibs]: https://github.com/tensorflow/mlir/tree/master/lib/Dialect/SPIRV
 [MlirSpirvTests]: https://github.com/tensorflow/mlir/tree/master/test/Dialect/SPIRV
 [MlirSpirvUnittests]: https://github.com/tensorflow/mlir/tree/master/unittests/Dialect/SPIRV
 [MlirGpuToSpirvHeaders]: https://github.com/tensorflow/mlir/tree/master/include/mlir/Conversion/GPUToSPIRV
 [MlirGpuToSpirvLibs]: https://github.com/tensorflow/mlir/tree/master/lib/Conversion/GPUToSPIRV
 [MlirStdToSpirvHeaders]: https://github.com/tensorflow/mlir/tree/master/include/mlir/Conversion/StandardToSPIRV
 [MlirStdToSpirvLibs]: https://github.com/tensorflow/mlir/tree/master/lib/Conversion/StandardToSPIRV
-[MlirSpirvDialect]: https://github.com/tensorflow/mlir/blob/master/include/mlir/Dialect/SPIRV/SPIRVDialect.h
-[MlirSpirvTypes]: https://github.com/tensorflow/mlir/blob/master/include/mlir/Dialect/SPIRV/SPIRVTypes.h
-[MlirSpirvOps]: https://github.com/tensorflow/mlir/blob/master/include/mlir/Dialect/SPIRV/SPIRVOps.h
-[MlirSpirvSerialization]: https://github.com/tensorflow/mlir/blob/master/include/mlir/Dialect/SPIRV/Serialization.h
-[MlirSpirvBase]: https://github.com/tensorflow/mlir/blob/master/include/mlir/Dialect/SPIRV/SPIRVBase.td
-[MlirSpirvPasses]: https://github.com/tensorflow/mlir/blob/master/include/mlir/Dialect/SPIRV/Passes.h
-[MlirSpirvLowering]: https://github.com/tensorflow/mlir/blob/master/include/mlir/Dialect/SPIRV/SPIRVLowering.h
-[MlirSpirvAbi]: https://github.com/tensorflow/mlir/blob/master/include/mlir/Dialect/SPIRV/SPIRVLowering.td
+[MlirSpirvDialect]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/SPIRVDialect.h
+[MlirSpirvTypes]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/SPIRVTypes.h
+[MlirSpirvOps]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/SPIRVOps.h
+[MlirSpirvSerialization]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/Serialization.h
+[MlirSpirvBase]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/SPIRVBase.td
+[MlirSpirvPasses]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/Passes.h
+[MlirSpirvLowering]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/SPIRVLowering.h
+[MlirSpirvAbi]: https://github.com/llvm/llvm-project/blob/master/mlir/include/mlir/Dialect/SPIRV/SPIRVLowering.td
 [GitHubDialectTracking]: https://github.com/tensorflow/mlir/issues/302
 [GitHubLoweringTracking]: https://github.com/tensorflow/mlir/issues/303
-[GenSpirvUtilsPy]: https://github.com/tensorflow/mlir/blob/master/utils/spirv/gen_spirv_dialect.py
+[GenSpirvUtilsPy]: https://github.com/llvm/llvm-project/blob/master/mlir/utils/spirv/gen_spirv_dialect.py
+[LlvmMlirSpirvDoc]: https://mlir.llvm.org/docs/Dialects/SPIRVOps/