watchdog: dw_wdt: ping watchdog to reset countdown before start

Currently on an rk3288 SoC when trying to use the watchdog the SoC will
instantly reset. This is due to the watchdog countdown counter being set
to its initial value of 0x0. Reset the watchdog counter before start in
order to correctly start the countdown timer from the right position.

Signed-off-by: Jack Mitchell <ml@embed.me.uk>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20200107155155.278521-1-ml@embed.me.uk


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>