ARM: dts: imx6qdl-nitrogen6x: add Okaya LCD panel

This patch adds support for the 7" LCD display available for Nitrogen6x:
http://boundarydevices.com/product/7-800x480-display/



Also add label to backlight_lcd and connect it to the panel.

Signed-off-by: Gary Bisson <gary.bisson@boundarydevices.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>