[llvm] [PowerPC] Ensure MI peephole knows about instr modified by combineRLWINM() (PR #97134)

[Chen Zheng via llvm-commits]

https://github.com/chenzheng1030 approved this pull request.

LGTM. Thanks for the fix. If we continue to meet new issues related to killed/dead flag setting, we may need another more generic way to improve this. See my inline comments below.

https://github.com/llvm/llvm-project/pull/97134