[llvm] [SDAG] Merge multiple-result libcall expansion into DAG.expandMultipleResultFPLibCall() (PR #114792)

[Benjamin Maxwell via llvm-commits]

MacDue wrote:

> I don't know if there's any better to suggest for the CopyFromReg that is optimised away when it has no uses, but it doesn't seem to break or regress anything either. So overall LGTM.

Given that the workaround here has been in the repo for about a year, I think it should be safe :slightly_smiling_face: 

https://github.com/llvm/llvm-project/pull/114792