[llvm] [AMDGPU][GlobalISel] Lower G_FMINIMUM and G_FMAXIMUM (PR #151122)

[Matt Arsenault via llvm-commits]

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

LGTM, but can you fix flag propagation in a follow up 

https://github.com/llvm/llvm-project/pull/151122