[llvm] [APFloat] Fix sign bit corrupting exponent in unsigned FP8 formats (PR #223286)

[Cheng-Chieh Liu via llvm-commits]

jay87406 wrote:

Thanks for the approval @tgymnich and @Tim096! Since I don't have write access yet, could someone help land this? Much appreciated.

https://github.com/llvm/llvm-project/pull/223286