pm2301: Update watchdog for pm2xxx support

AB and PMxxx doesn't have same watchdog refresh period. Add watchdog
to refresh period parameters in x500 charger structure, this should
kick watchdog every 30sec. The AC charging should also kick both
pm2xxx and the AB charger watchdog.

Signed-off-by: Rajkumar Kasirajan <rajkumar.kasirajan@stericsson.com>
Signed-off-by: Loic Pallardy <loic.pallardy@stericsson.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Michel JAOUEN <michel.jaouen@stericsson.com>
Reviewed-by: Marcus COOPER <marcus.xm.cooper@stericsson.com>
Reviewed-by: Jonas ABERG <jonas.aberg@stericsson.com>
Tested-by: Michel JAOUEN <michel.jaouen@stericsson.com>
Tested-by: Jonas ABERG <jonas.aberg@stericsson.com>