watchdog: atmel: atmel-sama5d4-wdt: Disable watchdog on system suspend

Currently, the atmel-sama5d4-wdt continues to run after system suspend.
Unless the system resumes within the watchdog timeout period so the
userspace can kick it, the system will be reset. This change disables
the watchdog on suspend if it is active and re-enables on resume. These
actions occur during the late and early phases of suspend and resume
respectively to minimize chances where a lock could occur while the
watchdog is disabled.

Signed-off-by: Ken Sloat <ksloat@aampglobal.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>