[binutils][aarch64] New sve_shift_tsz_bhsd iclass.

[binutils][aarch64] New sve_shift_tsz_bhsd iclass.

This new iclass encodes the variant by which is the most significant bit
used of bits 23-22:20-19, where those bits are usually part of a
given constant operand.

include/ChangeLog:

2019-05-09  Matthew Malcomson  <matthew.malcomson@arm.com>

	* opcode/aarch64.h (enum aarch64_insn_class): Add sve_shift_tsz_bhsd
	iclass.

opcodes/ChangeLog:

2019-05-09  Matthew Malcomson  <matthew.malcomson@arm.com>

	* aarch64-asm.c (aarch64_encode_variant_using_iclass): Handle
	sve_shift_tsz_bhsd iclass encode.
	* aarch64-dis.c (aarch64_decode_variant_using_iclass): Handle
	sve_shift_tsz_bhsd iclass decode.