[libc] [llvm] [libc][math] Refactor logf16 to header-only shared math (PR #175408)

[Muhammad Bassiouni via llvm-commits]

https://github.com/bassiounix requested changes to this pull request.

Thank you for your PR. You are on the right track with some nit.

https://github.com/llvm/llvm-project/pull/175408