ARM: dts: imx6q: Add Variscite DART-MX6 Carrier-board support

ARM: dts: imx6q: Add Variscite DART-MX6 Carrier-board support

This patch adds support for the i.MX6 Quad variant of the Variscite DART-MX6
SoM Carrier-Board.

This Carrier-Board has the following :
- LVDS interface for the VLCD-CAP-GLD-LVDS 7" LCD 800 x 480 touch display
- HDMI Connector
- USB Host + USB OTG Connector
- 10/100/1000 Mbps Ethernet
- miniPCI-Express slot
- SD Card connector
- Audio Headphone/Line In jack connectors
- On-board DMIC
- CAN bus header
- SPI header
- Camera Interfaces header
- 4xButtons, 2xLeds
- OnBoard RTC with Coin Backup battery socket
- RS232 Header + USB-Serial debug port

Product Page : http://www.variscite.com/products/evaluation-kits/dart-mx6-kits

The board support is done with all on-board and header interfaces enabled.
7" LVDS Touchscreen is enabled by default along HDMI output.
Audio interface is supported with the "simple-card" bindings.

PCIe slot, On-Board DMIC and Camera Interfaces are not handled yet.

Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>