aarch64: Add BC instruction

aarch64: Add BC instruction

This patch adds support for the Armv8.8-A BC instruction.
[https://developer.arm.com/documentation/ddi0596/2021-09/Base-Instructions/BC-cond--Branch-Consistent-conditionally-?lang=en]

include/
	* opcode/aarch64.h (AARCH64_FEATURE_HBC): New macro.
	(AARCH64_ARCH_V8_8): Make armv8.8-a imply AARCH64_FEATURE_HBC.

opcodes/
	* aarch64-tbl.h (aarch64_feature_hbc): New variable.
	(HBC, HBC_INSN): New macros.
	(aarch64_opcode_table): Add BC.C.
	* aarch64-dis-2.c: Regenerate.

gas/
	* doc/c-aarch64.texi: Document +hbc.
	* config/tc-aarch64.c (aarch64_features): Add "hbc".
	* testsuite/gas/aarch64/hbc.s, testsuite/gas/aarch64/hbc.d: New test.
	* testsuite/gas/aarch64/hbc-invalid.s,
	testsuite/gas/aarch64/hbc-invalid.l,
	testsuite/gas/aarch64/hbc-invalid.d: New test.