aarch64: [SME] Add +sme option to -march

aarch64: [SME] Add +sme option to -march

This series of patches (tagged [SME]) add support for the Scalable
Matrix Extension. Patch introduces new command line options: +sme, +sme-f64 and
+sme-i64 to -march command line options.

gas/ChangeLog:

	* NEWS: Updated docs.
	* config/tc-aarch64.c: New SME command line options.
	* doc/c-aarch64.texi: Update docs.

include/ChangeLog:

	* opcode/aarch64.h (AARCH64_FEATURE_SME): New flag.
	(AARCH64_FEATURE_SME_F64): New flag.
	(AARCH64_FEATURE_SME_I64): New flag.

opcodes/ChangeLog:

	* aarch64-tbl.h (SME): New feature object.