[llvm] [PHIElimination] Fix bug around $noreg assignment (PR #146320)

[Mikael Holmén via llvm-commits]

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

Thanks for the quick fix!
I've verified that this solves the problem I reported in https://github.com/llvm/llvm-project/pull/131837#issuecomment-3018167771

Maybe you want someone who reviewed the original change to look at this too, but as far as I'm concerned this looks ok.

https://github.com/llvm/llvm-project/pull/146320