[llvm] [AMDGPU] Simplify OtherPredicates handling in MadFmaMixPats. NFC. (PR #127044)

[Joe Nash via llvm-commits]

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

LGTM. The previous style was a relic from before we had True16Predicate.

https://github.com/llvm/llvm-project/pull/127044