ARM: dts: imx: Add support for Logic PD i.MX6QD EVM

The EVM consists of a system on module (SOM) and baseboard, and LCD.
This patch adds a DTSI file for the SOM and baseboard separately,
then a wrapper to combine them and specify processor type and a
LCD information.

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>