[mlir][gpu] Allow all dialects in SCF to GPU conversion.

[herhut]

Summary

With the standard dialect being split up, the set of dialects that are
used when converting to GPU is growing. This change modifies the
SCFToGpu pass to allow all operations inside launch bodies.

mlir/lib/Conversion/SCFToGPU/SCFToGPUPass.cpp

 };
 
 struct ParallelLoopToGpuPass
     : public ConvertParallelLoopToGpuBase<ParallelLoopToGpuPass> {
   void runOnOperation() override {
     OwningRewritePatternList patterns;
     populateParallelLoopToGPUPatterns(patterns, &getContext());
     ConversionTarget target(getContext());
-    target.addLegalDialect<AffineDialect, complex::ComplexDialect,
-                           gpu::GPUDialect, scf::SCFDialect,
-                           StandardOpsDialect>();
+    target.markUnknownOpDynamicallyLegal([](Operation *) { return true; });
     configureParallelLoopToGPULegality(target);
     if (failed(applyPartialConversion(getOperation(), target,
                                       std::move(patterns))))
       signalPassFailure();
   }
 };
 
 } // namespace