aarch64: Add 128-bit system register flags

aarch64: Add 128-bit system register flags

In preparation for the implementation of 128-bit system register
support across the toolchain, this patch adds the feature flag
F_REG_128 and adds it to relevant system registers in
`aarch64-sys-regs.def'.

Given the shared nature of this file, this change is made necessary
initially to implement argument validation in the `__arm_rsr128' and
`__armwsr128' ACLE intrinsics in GCC, but will be of subsequent use in
the binutils implementation of the corresponding `mrrs' and `msrr'
instructions.

Regression tested on aarch64-linux-gnu, no regressions.

opcodes/ChangeLog:

	* aarch64-opc.h (F_REG_128):  New flag.
	* aarch64-sys-regs.def (par_el1): Add F_REG_128 flag.
	(rcwmask_el1): Likewise.
	(rcwsmask_el1): Likewise.
	(ttbr0_el1): Likewise.
	(ttbr0_el12): Likewise.
	(ttbr0_el2): Likewise.
	(ttbr1_el1): Likewise.
	(ttbr1_el12): Likewise.
	(ttbr1_el2): Likewise.
	(vttbr_el2): Likewise.