[llvm] [PowerPC] Forbid f128 SELECT_CC optimized into fsel (PR #71497)

[Chen Zheng via llvm-commits]

https://github.com/chenzheng1030 approved this pull request.

This seems reasonable to me. 
Please wait for one day in case @lei137 has other concerns. Thanks for fixing this.

https://github.com/llvm/llvm-project/pull/71497