[AArch64][SVE2] Asm: support SVE2 Floating Point Pairwise Group

Summary:
Patch adds support for the following instructions:

SVE2 floating-point pairwise operations:
    * FADDP, FMAXNMP, FMINNMP, FMAXP, FMINP

The specification can be found here:
https://developer.arm.com/docs/ddi0602/latest

Reviewed By: chill

Differential Revision: https://reviews.llvm.org/D62383

llvm-svn: 361933