[AArch64][SVE2] Asm: support SVE2 Misc Group

Summary:
Patch adds support for the following instructions:

SVE2 bitwise exclusive-or interleaved:
    * EORBT, EORTB

SVE2 bitwise permute:
    * BEXT, BDEP, BGRP

SVE2 bitwise shift left long:
    * SSHLLB, SSHLLT, USHLLB, USHLLT

SVE2 integer add/subtract interleaved long:
    * SADDLBT, SSUBLBT, SSUBLTB

BDEP, BEXT and BGRP are enabled with SVE2 feature +bitperm, all other
instructions in this group are enabled with +sve2.

Reviewed By: chill

Differential Revision: https://reviews.llvm.org/D62304

llvm-svn: 361795