[PATCH, BINUTILS, ARM] Add SSBB and PSSBB

[Nick Clifton]

Hi Sudi,

> Sorry I forgot to ask before. Would it be possible to backport
> to 2.31? It applies cleanly and I have ran regression tests and
> see no failures.

Normally the answer would be "no", since this is adding a new feature.
I can guess the importance of supporting these instructions however,
so this one time I am going to make an exception and allow it.

Patch applied to the 2.31 branch.

Cheers
  Nick