[llvm] [AMDGPU][Verifier] Limit kill/wqm.demote intrinsics to PS shaders (PR #151922)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

We should be generalizing kill support. In particular this should work in callable functions. Restricting to a specific entry point is bad 

https://github.com/llvm/llvm-project/pull/151922