[AArch64] Add support for NEON scalar arithmetic instructions:
SQDMULH, SQRDMULH, FMULX, FRECPS, and FRSQRTS.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192107 91177308-0d34-0410-b5e6-96231b3b80d8