[llvm] [SDAG] Add missing ppc_fp128 ExpandFloatRes legalization for modf (PR #127895)

[Vitaly Buka via llvm-commits]

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

LGTM, but I don't know this code.
If you need a real review, better to revert and reland with a fix.

https://github.com/llvm/llvm-project/pull/127895