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 <[e-mail]>
Cc: Pawel Moll <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Ian Campbell <[e-mail]>
Cc: Kumar Gala <[e-mail]>

Documentation/devicetree/bindings/mfd/sky81452.txt

···
 
 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