[llvm] [AMDGPU] Detect kills in register sets when trying to form V_CMPX instructions. (PR #68293)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

Can you just drop kill flags without prejudice? We shouldn't really need them anymore at this point 

https://github.com/llvm/llvm-project/pull/68293