watchdog: imx7ulp: Watchdog should continue running for wait/stop mode

When kernel idle, system will enter wait/stop mode, wdog should continue
running in this scenario, and the refresh thread can wake up system from
wait/stop mode.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/1596150213-31638-2-git-send-email-Anson.Huang@nxp.com


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