[GlobalISel][AArch64] Legalize vector G_FPOW

This instruction is legalized in the same way as G_FSIN, G_FCOS, G_FLOG10, etc.

Update legalize-pow.mir and arm64-vfloatintrinsics.ll to reflect the change.

Differential Revision: https://reviews.llvm.org/D60218

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@358764 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed