arm64: dts: imx: Add i.MX8M Plus Gateworks GW82XX-2X support

The Gateworks GW82XX-2X is an ARM based single board computer (SBC)
comprised of the i.MX8M Plus based gw702x SoM and the gw82xx baseboard
featuring:
 - i.MX8M Plus SoC
 - LPDDR4 DRAM
 - eMMC FLASH
 - Gateworks System Controller (GSC)
 - microSD (1.8V/3.3V Capable)
 - panel status bi-color LED
 - pushbutton switch
 - fan controller with tachometer
 - USB Type-C connector
 - PCIe switch
 - 2x GbE RJ45 connectors
 - multi-protocol RS232/RS485/RS422 Serial ports
 - 2x Flexible Socket Adapters with SDIO/UART/USB/PCIe
   (for M.2 and miniPCIe expansion)
 - 2x isolated CAN
 - GPS
 - accelerometer
 - magnetometer
 - off-board connectors for: SPI, GPIO, I2C, ADC
 - Wide range DC power input
 - support for 802.3at PoE (via adapter)

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>