imx: ventana: add GW5912 support

imx: ventana: add GW5912 support

The GW5912 is a Single Board Computer based on the NXP i.MX6Q/DL SoC
with the following features:
 - DDR3 DRAM
 - NAND FLASH (256MiB or 2048MiB)
 - microSD socket
 - Gateworks System Periperhal Controller
 - front panel LED's
 - front panel pushbutton
 - RS232 connector (2x UARTs)
 - CAN/RS485 connector
 - Digital I/O connector (I2C/GPIO)
 - SPI connector
 - u-blox Zoe-M8Q GPS
 - LIS2DE12 Accellerometer
 - 1x FEC GbE RJ45 with 802.3at Active PoE
 - 1x PCI GbE RJ45 with Passive PoE
 - 5x MiniPCIe socket with PCIe/USB 2.0
 - 1x MiniPCIe socket with PCIe/USB 2.0 and SIM socket
 - Aux power input with wide-range DC power supply

Signed-off-by: Tim Harvey <tharvey@gateworks.com>