[llvm] Enable logf128 constant folding for hosts with 128bit long double (PR #104929)

[David Green via llvm-commits]

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

Thanks for checking, thats good to hear. The changes LGTM, with a suggestion to common some code even if it doesn't end up in a header.

https://github.com/llvm/llvm-project/pull/104929