watchdog: diag288_wdt: remove power management

Remove power management because s390 no longer supports hibernation since
commit 39421627

 ("s390: remove broken hibernate / power management
support").

Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230203073958.1585738-3-egorenar@linux.ibm.com


Signed-off-by: Heiko Carstens <hca@linux.ibm.com>