watchdog: Add watchdog timer support for the WinSystems EBC-C384

The WinSystems EBC-C384 has an onboard watchdog timer. The timeout range
supported by the watchdog timer is 1 second to 255 minutes. Timeouts
under 256 seconds have a 1 second granularity, while the rest have a 1
minute granularity.

This driver adds watchdog timer support for this onboard watchdog timer.
The timeout may be configured via the timeout module parameter.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>