PM / watchdog: iTCO: stop watchdog during system suspend

If the target sleep state of the system is not an ACPI sleep state
(S1, S2 or S3), the TCO watchdog needs to be stopped during system
suspend, because it may not be possible to ping it any more after
timekeeping has been suspended (suspend-to-idle does that for
one example).

For this reason, provide ->suspend_noirq and ->resume_noirq
callbacks for the iTCO watchdog driver and use them to stop
and restart the watchdog during system suspend and resume,
respectively, if the system is not going to enter an ACPI
sleep state (in which case the watchdog will be stopped
by the platform firmware before the state is entered).

Reported-and-tested-by: Borun Fu <borun.fu@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>