[llvm] [AMDGPU] Do not erase KILLs that redefine a register in SIPostRABundler (PR #218349)

[Jay Foad via llvm-commits]

jayfoad wrote:

Do you have an IR test case that fails because of this? Does it fail machine verification if the KILL gets erased?

https://github.com/llvm/llvm-project/pull/218349