[llvm] [X86] Fix miscompile of fptosi.sat.iN.f16 for NaN under avx512fp16 (PR #210556)

[Nikita Popov via llvm-commits]

nikic wrote:

Please omit any extraneous information from PR descriptions and code comments.

(Information about tests is nearly always unnecessary.)

https://github.com/llvm/llvm-project/pull/210556