[Aarch64] Support an ARMv8.2 system register.

[Aarch64] Support an ARMv8.2 system register.

ARMv8.2 adds a new system register id_aa64mmfr2_el1. This patch adds
support for the register to binutils, making it available when
-march=armv8.2-a is selected.

opcodes/
2015-11-27  Matthew Wahab  <matthew.wahab@arm.com>

	* aarch64-opc.c (aarch64_sys_regs): Add "id_aa64mmfr2_el1".
	(aarch64_sys_reg_supported_p): Add ARMv8.2 system register
	feature test.

gas/testsuite/
2015-11-27  Matthew Wahab  <matthew.wahab@arm.com>

	* gas/aarch64/sysreg-2.d: New.
	* gas/aarch64/sysreg-2.s: New.

Change-Id: I767f18a60e2bd70ce74c89f6abfe07afdc9e601f