watchdog: convert remaining drivers to use SPDX license identifier

This gets rid of the unnecessary license boilerplate, and avoids
having to deal with individual patches one by one.

No functional changes.

Reviewed-by: Jerry Hoemann <jerry.hoemann@hpe.com>
Acked-by: Sylvain Lemieux <slemieux.tyco@gmail.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/omap_wdt.c

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * omap_wdt.c
  *
@@ -6,10 +7,7 @@
  * Author: MontaVista Software, Inc.
  *	 <gdavis@mvista.com> or <source@mvista.com>
  *
- * 2003 (c) MontaVista Software, Inc. This file is licensed under the
- * terms of the GNU General Public License version 2. This program is
- * licensed "as is" without any warranty of any kind, whether express
- * or implied.
+ * 2003 (c) MontaVista Software, Inc.
  *
  * History:
  *