[llvm] Reapply "[AMDGPU][MC] Allow op_sel in v_alignbit_b32 etc in GFX9 and … (PR #149262)

[Joe Nash via llvm-commits]

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

It should remove [MC] from the commit title, and add 'NFCI to codegen' to the commit body. 

Otherwise LGTM

https://github.com/llvm/llvm-project/pull/149262