aarch64: Add the SME2 MOVA instructions

aarch64: Add the SME2 MOVA instructions

SME2 defines new MOVA instructions for moving multiple registers
to and from ZA.  As with SME, the instructions are also available
through MOV aliases.

One notable feature of these instructions (and many other SME2
instructions) is that some register lists must start at a multiple
of the list's size.  The patch uses the general error "start register
out of range" when this constraint isn't met, rather than an error
specifically about multiples.  This ensures that the error is
consistent between these simple consecutive lists and later
strided lists, for which the requirements aren't a simple multiple.