sme2: signal frame support

Teach gdb about the ZT state on signal frames and how to restore
the contents of the registers.

There is a new ZT_MAGIC context that the Linux Kernel uses to communicate
the ZT register state to gdb.

As mentioned before, the ZT state should only be available when the ZA state
is available.

Validated under Fast Models.

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
1 file changed