wl18xx: read FW pc on recovery

Define the FW pc in the 18xx register translation table. This specific
register is only valid in the boot partition, so change the momentarily
change partitions. This doesn't damage 12xx cards, where the FW pc is
accessible via boot partition as well.

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>