MAINTAINERS: Add file patterns for led 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>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: linux-leds@vger.kernel.org
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>

MAINTAINERS

@@ -6708,6 +6708,7 @@ M:	Jacek Anaszewski <j.anaszewski@samsung.com>
 L:	linux-leds@vger.kernel.org
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/j.anaszewski/linux-leds.git
 S:	Maintained
+F:	Documentation/devicetree/bindings/leds/
 F:	drivers/leds/
 F:	include/linux/leds.h