ARM: dts: add imx7d soc dtsi file

imx7d intergrates the unique display controller for EPD panel, pixel engines
and graphics engines to make it a ideal solution for EPD based devices such
as eReader, Signage, as well as any application rely on the bistable charactersic
of the EPD panel.

imx7d include two ARM Cortex A7 Core and one Cortex-M4 core.
Included Main Peripheral
 - DDR3\LP-DDR2
 - GPMI\BCH\APBH DMA(NAND flash support)
 - QSPI
 - WEIM Nor
 - LCDIF\MIPI DSI
 - CSI\MIPI CSI
 - EPDC
 - PCIe RC\EP
 - USB OTG\Host
 - CAN x2
 - I2C x4
 - SIMv2 x2
 - ENET -x2
 - uSDHC x3
 - eCSPI x1
 - PWM x4
 - OCOTP (fuse)
 - GPT x4
 - WDOG x4
 - Flex Timer x2

Signed-off-by: Anson Huang <[email protected]>
Signed-off-by: Frank Li <[email protected]>
Signed-off-by: Shawn Guo <[email protected]>