[llvm] [GlobalISel][AArch64][AMDGPU] Preserve saturation bounds when narrowing fp-to-int (PR #215567)

[Nathaniel McCallum via llvm-commits]

npmccallum wrote:

@perlfu I think we probably need another review pass from you now that the GlobalISel changes seem to be in good shape.

https://github.com/llvm/llvm-project/pull/215567