GlobalISel: IRTranslate llvm.fmuladd.* intrinsic

Reviewers: qcolombet, ab, dsanders, aditya_nandakumar, bogner

Reviewed By: qcolombet

Subscribers: rovka, kristof.beyls, javed.absar, llvm-commits

Differential Revision: https://reviews.llvm.org/D43090

llvm-svn: 324971