hw/ppc: pnv_core.c add vmstate support

hw/ppc: pnv_core.c add vmstate support

- Add vmstate support PnvCore and PnvQuad capturing scratch
registers and special wakeup registers

Signed-off-by: Angelo Jaramillo <angelo.jaramillo@linux.ibm.com>
Reviewed-by: Glenn Miles <milesg@linux.ibm.com>
Reviewed-by: Aditya Gupta <adityag@linux.ibm.com>
Reviewed-by: Chalapathi V <chalapathi.v@linux.ibm.com>
Signed-off-by: Caleb Schlossin <calebs@linux.ibm.com>
Link: https://lore.kernel.org/qemu-devel/20260105160138.3242709-6-calebs@linux.ibm.com
Signed-off-by: Harsh Prateek Bora <harshpb@linux.ibm.com>