dt-bindings: arm: imx: Add i.mx6q DaSheng COM-9XX SBC

The DaSheng Com-9xx is and ARM based signle board computer (SBC)
featuring:
- i.MX6Q
- 2GiB LPDDR3 DRAM
- 8GiB eMMC 5.0 FLASH
- 4MiB SPI Flash
- USB 2.0 Host/Device
- Multiple multi-protocol RS232/RS485 Serial ports
- microSD socket
- 5V DC power input
- HDMI1.4a,1080p@60
- RGMIIx1 Gigabit Ethernet
- CSI0x1, connect with ov2659

Signed-off-by: Dillon Min <dillon.minfei@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>