[Aarch64][binutils] Support id_mmfr4 system register.

[Nicholas Clifton]

Hi Matthew,

> opcodes/
> 2015-06-16  Matthew Wahab  <matthew.wahab@arm.com>
>
>      * aarch64-opc.c (aarch64_sys_regs): Add "id_mmfr4_el1".
>
> gas/testsuite
> 2015-06-16  Matthew Wahab  <matthew.wahab@arm.com>
>
>      * sysreg.d: Add id_mmfr4_el1, update expected output.
>      * sysreg.s: Add id_mmfr4_el1.

Approved - please apply.

Cheers
   Nick