watchdog: da9062: Disable and wait before changing timeout

The DA9062 watchdog occasionally enters error condition and resets the
system if the timeout is changed quickly after the timer was enabled.

The method of disabling and waiting for > 150 µs before setting the
new timeout is taken from the DA9052 driver.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>