watchdog: orion: make license info match the file header

The header says: This file is licensed under the terms of the GNU
General Public License version 2. The right identifier for
MODULE_LICENSE is "GPL v2" then.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
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>