[llvm] [AMDGPU] Add GFX12 llvm.amdgcn.s.wait.*cnt intrinsics (PR #78723)

[Jay Foad via llvm-commits]

jayfoad wrote:

This is by analogy with the existing `amdgcn.s.waitcnt` intrinsic. TBH I don't know if there is a good use case for the new intrinsics.

https://github.com/llvm/llvm-project/pull/78723