[llvm] [AMDGPU] Constant folding of llvm.amdgcn.trig.preop (PR #98562)

[Matt Arsenault via llvm-commits]

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

LGTM. I would feel better if we had some conformance testing with constant folding values, but we don't 

https://github.com/llvm/llvm-project/pull/98562