[llvm] [AMDGPU][GlobalISel] Align `selectVOP3PMadMixModsImpl` with the `SelectionDAG` counterpart (PR #110168)

[Shilei Tian via llvm-commits]

shiltian wrote:

Thanks @petar-avramovic . It indeed works. It might be better to do it in TableGen so I will probably make a follow-up patch. For now, I'd like to get the issue resolved such that another PR can be merged as well.

https://github.com/llvm/llvm-project/pull/110168