[PowerPC] Mark FCOPYSIGN legal for FP vectors

This was just an omission in the back end. We have had the instructions for both
single and double precision for a few HW generations, but never got around to
legalizing these.

Differential revision: https://reviews.llvm.org/D63634


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@364373 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed