[llvm] [ConstantFold] Fix result type when folding powi.f16 (PR #98681)

[Nikita Popov via llvm-commits]

https://github.com/nikic approved this pull request.

LGTM, though this code could really do with some cleanup. Why are there three different `if`s checking for `IntrinsicID == Intrinsic::powi` when there is a perfectly good `switch` just before it?

https://github.com/llvm/llvm-project/pull/98681