[llvm] [X86][LegalizeDAG] FPOWI: promote f16 operand (PR #105775)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

> Add a test case (probably to avx512fp16-scalar.ll ?)

I've added fp16-libcalls.ll which should give us better test coverage - please add the powi tests there

https://github.com/llvm/llvm-project/pull/105775