Maxim PMIC MAX77620 is Power management IC which have multiple
sub blocks like regulators (DCDC/LDOs), GPIO, RTC, Clock, Watchdog
timer etc.

Add the driver for watchdog timer under watchdog framework.
The driver implements the watchdog callbacks to start, stop,
ping and set timeout for watchodg framework.
Signed-off-by: NLaxman Dewangan <ldewangan@nvidia.com>
Reviewed-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NWim Van Sebroeck <wim@iguana.be>