[llvm] [GlobalISel][AArch64][AMDGPU] Don't narrow saturating fp-to-int conversions (PR #215567)

[Carl Ritson via llvm-commits]

https://github.com/perlfu commented:

AMDGPU test changes make sense to be, w.r.t. PR description.
Not sure I cannot comment on the rest.

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