[clang] [llvm] [llvm][AMDGPU] Fold `llvm.amdgcn.wavefrontsize` early (PR #114481)

[Matt Arsenault via cfe-commits]

arsenm wrote:

#117410 gives you a way to do this without explicitly looking at the features or CPU 

https://github.com/llvm/llvm-project/pull/114481