aspeed: watchdog: Set bootstatus during probe

Check the aspeed timeout status register to see if the system has booted
from the secondary boot source. If so, set the watchdog device
bootstatus flag for "Card previously reset the CPU."

Signed-off-by: Eddie James <eajames@linux.vnet.ibm.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@iguana.be>