aarch64: add armv9-a architecture to -march

Patch is adding new 'armv9-a` command line flag to -march for AArch64.

gas/

	* config/tc-aarch64.c: Add 'armv9-a' command line flag.
	* docs/c-aarch64.text: Update docs.
	* NEWS: Update docs.

include/

	* opcode/aarch64.h (AARCH64_FEATURE_V9): New define.
	(AARCH64_ARCH_V9): New define.
4 files changed