watchdog: wdat_wdt: fix get_timeleft call for wdat_wdt

The get_timeleft call for wdat_wdt was using ACPI_WDAT_GET_COUNTDOWN
when running an action on the device, which would return the configured
countdown, instead of ACPI_WDAT_GET_CURRENT_COUNTDOWN, which returns the
time left before the watchdog will fire. This change corrects that.

Signed-off-by: Bryan Tan <bryantan@vmware.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>