MAINTAINERS: Add file patterns for watchdog device tree bindings

Submitters of device tree binding documentation may forget to CC
the subsystem maintainer if this is missing.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Cc: linux-watchdog@vger.kernel.org

MAINTAINERS

@@ -12073,6 +12073,7 @@ L:	linux-watchdog@vger.kernel.org
 W:	http://www.linux-watchdog.org/
 T:	git git://www.linux-watchdog.org/linux-watchdog.git
 S:	Maintained
+F:	Documentation/devicetree/bindings/watchdog/
 F:	Documentation/watchdog/
 F:	drivers/watchdog/
 F:	include/linux/watchdog.h