[llvm] [AMDGPU] In instruction selector, allow copy from physical reg to s1 (PR #96157)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm requested changes to this pull request.

isVCC needs to gain a new parameter for the partnered register in the copy. There shouldn't be any need to fixup the result after, or check register class membership 

https://github.com/llvm/llvm-project/pull/96157