[Patch AArch64] Add support for Cortex-A55 and Cortex-A75

[Nick Clifton]

Hi James,

> 2017-06-08  James Greenhalgh  <james.greenhalgh@arm.com>
> 
> 	* config/tc-aarch64.c (aarch64_cpus): Add cortex-a55 and cortex-a75.
> 	* doc/c-aarch64.texi (-mcpu): Document cortex-a55 and cortex-a75.

Approved and applied.  Sorry for the delay in responding.

Cheers
  Nick