[llvm] [AMDGPU] Use `v_cvt_pk_*` instructions for i16_f32 saturated conversions (PR #202680)

[Igor Wodiany via llvm-commits]

IgWod wrote:

Fix for buildbot failure (https://lab.llvm.org/buildbot/#/builders/187/builds/21241) in #202680.

https://github.com/llvm/llvm-project/pull/202680