target-microblaze: Preserve the pvr registers during reset

target-microblaze: Preserve the pvr registers during reset

Move the Microblaze PVR registers to the end of the CPUMBState
and preserve them during reset. This is similar to what the
QEMU ARM model does with some of it's registers.

This allows the Microblaze PVR registers to only be set once
at realise instead of constantly at reset.

Signed-off-by: Alistair Francis <[email protected]>
Reviewed-by: Peter Crosthwaite <[email protected]>
Reviewed-by: Edgar E. Iglesias <[email protected]>
Signed-off-by: Edgar E. Iglesias <[email protected]>