[PATCH 2/3][Binutils] aarch64: Add support for GCSB DSYNC instruction.

[Nick Clifton]

Hi Srinath,

> This patch adds support for Guarded control stack data synchronization
> instruction (GCSB DSYNC). This instruction is allocated to existing
> HINT space and uses the HINT number 19 and to match this an entry is
> added to the aarch64_hint_options array.
> 
> Regression tested for aarch64-none-elf target and found no regressions.
> 
> Ok for binutils-master?

Approved - please apply.

Cheers
   Nick

PS.  I was a little bit confused at first because it looked like you were
   replacing specific syntax error messages, eg ""unknown or missing option
   to PSB/TSB", with more generic ones.  But then I read a little bit further
   into the patch and saw the test for the actual error messages.