[llvm] [SDISel][Combine] Constant fold FP16_TO_FP (PR #94790)

[Quentin Colombet via llvm-commits]

qcolombet wrote:

@arsenm @phoebewang This is the fix for the "perf" regression exposed by the correctness fix from https://github.com/llvm/llvm-project/pull/94591.

https://github.com/llvm/llvm-project/pull/94790