[PATCH][GAS] aarch64: Update LS64 feature with system register

[Nick Clifton]

Hi Przemyslaw,
  
> OK for master branch?

Approved - please apply.

Cheers
   Nick

> gas/ChangeLog:
> 2020-11-05  Przemyslaw Wirkus  <mailto:przemyslaw.wirkus@arm.com>
> 
> 	* testsuite/gas/aarch64/ls64.d: New test.
> 	* testsuite/gas/aarch64/ls64.s: Test for ACCDATA_EL1 register.
> 
> opcodes/ChangeLog:
> 2020-11-05  Przemyslaw Wirkus  <mailto:przemyslaw.wirkus@arm.com>
> 
> 	* aarch64-opc.c: Add ACCDATA_EL1 system register