[llvm] [RegisterScavenging] Respect early-clobber when scavenging registers (PR #184814)

[Dominik Steenken via llvm-commits]

dominik-steenken wrote:

I fixed an issue where the iteration across MBBI operands wasn't safeguarded against MBBI being a sentinel. I also made a (hopefully) very minor fix to an AMDGPU test case where i think this fix just changed the choice of register slightly.

https://github.com/llvm/llvm-project/pull/184814