[clang] [llvm] [mlir] [AMDGPU] Verify AMDGPU required workgroup size matches flat workgroup size (PR #200989)

[Matt Arsenault via cfe-commits]

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+; RUN: split-file %s %t
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arsenm wrote:

This should be moved out of AMDGPU 

https://github.com/llvm/llvm-project/pull/200989