[AArch64] Fix ARMv8.1 and ARMv8.2 feature settings.

[AArch64] Fix ARMv8.1 and ARMv8.2 feature settings.

ARMv8.1 includes CRC as a required extension but this isn't reflected in
the features enabled by -march=armv8.1-a. The FP16 feature modifier also
clashes with AARCH64_FEATURE_V8_1 and the list of features for ARMv8.2
is missing ARMv8.1 features.

This patch enables +crc for -march values of armv8.1-a and later. It
also fixes the values for AARCH64_FEATURE_F16 and makes
AARCH64_ARCH_V8_2 and superset of AARCH64_ARCH_V8_2.

gas/
2015-12-10  Matthew Wahab  <matthew.wahab@arm.com>

	* doc/c-aarch64.texi (AArch64 Extensions): Update entry for crc.

include/opcode
2015-12-10  Matthew Wahab  <matthew.wahab@arm.com>

	* aarch64.h (AARCH64_FEATURE_F16): Fix clash with
	AARCH64_FEATURE_V8_1.
	(AARCH64_ARCH_V8_1): Add AARCH64_FEATURE_CRC.
	(AARCH64_ARCH_V8_2): Add AARCH64_FEATURE_CRC and
	AARCH64_FEATURE_V8_1.

Change-Id: I8af5369f6df2430b28f6cec92870d2a4d14a7431