arm64: mops: handle MOPS exceptions

arm64: mops: handle MOPS exceptions

The memory copy/set instructions added as part of FEAT_MOPS can take an
exception (e.g. page fault) part-way through their execution and resume
execution afterwards.

If however the task is re-scheduled and execution resumes on a different
CPU, then the CPU may take a new type of exception to indicate this.
This is because the architecture allows two options (Option A and Option
B) to implement the instructions and a heterogeneous system can have
different implementations between CPUs.

In this case the OS has to reset the registers and restart execution
from the prologue instruction. The algorithm for doing this is provided
as part of the Arm ARM.

Add an exception handler for the new exception and wire it up for
userspace tasks.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Link: https://lore.kernel.org/r/20230509142235.3284028-8-kristina.martsenko@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>