dt-bindings: move backlight bindings under leds

Backlights are generally a subtype of LEDs at least from a software
point of view if not always electrically. Move the bindings from the
video directory to underneath the leds dir.
Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Kumar Gala <galak@codeaurora.org>

Documentation/devicetree/bindings/mfd/sky81452.txt

@@ -6,7 +6,7 @@ Required properties:
 
 Required child nodes:
 - backlight	: container node for backlight following the binding
-		in video/backlight/sky81452-backlight.txt
+		in leds/backlight/sky81452-backlight.txt
 - regulator	: container node for regulators following the binding
 		in regulator/sky81452-regulator.txt