[mlir][arith] Do not limit arith-expand pass to FuncOp

[Hardcode84]

Summary

This pass doesn't have any limitations specific to FuncOp and it will be useful to be able to run it on other ops (e.g. gpu.func).

[rriddle]

Please add proper justification to the patch description. It's important to capture the "why" in addition to the "what".

mlir/include/mlir/Dialect/Arithmetic/Transforms/Passes.td

def ArithmeticBufferize : Pass<"arith-bufferize", "ModuleOp"> {
   }];
   let constructor = "mlir::arith::createArithmeticBufferizePass()";
   let options = [
     Option<"alignment", "alignment", "unsigned", /*default=*/"0",
            "Create global memrefs with a specified alignment">,
   ];
 }
 
-def ArithmeticExpandOps : Pass<"arith-expand", "FuncOp"> {
+def ArithmeticExpandOps : Pass<"arith-expand"> {
   let summary = "Legalize Arithmetic ops to be convertible to LLVM.";
   let constructor = "mlir::arith::createArithmeticExpandOpsPass()";
   let dependentDialects = ["StandardOpsDialect"];
 }
 
 #endif // MLIR_DIALECT_ARITHMETIC_TRANSFORMS_PASSES