arm64: dts: imx8mm: Add Gateworks i.MX 8M Mini Development Kits

The Gateworks Venice GW71xx-0x/GW72xx-0x/GW73xx-0x are development
kits consisting of a GW700x SoM and a Baseboard. Future SoM's such
as the GW701x will create additional combinations.

The GW700x SoM contains:
 - i.MX 8M Mini SoC
 - LPDDR4 DRAM
 - eMMC FLASH
 - Gateworks System Controller (eeprom/pushbutton/reset/voltage-monitor)
 - GbE PHY connected to the i.MX 8M Mini FEC
 - Power Management IC

The GW71xx Baseboard contains:
 - 1x MiniPCIe Socket with USB2.0, PCIe, and SIM
 - 1x RJ45 GbE (i.MX 8M Mini FEC)
 - I/O connector with 1x-SPI/1x-I2C/1x-UART/4x-GPIO signals
 - PCIe Clock generator
 - GPS and accelerometer
 - 1x USB 2.0 Front Panel connector
 - wide range power supply

The GW72xx Baseboard contains:
 - 2x MiniPCIe Socket with USB2.0, PCIe, and SIM
 - 2x RJ45 GbE (i.MX 8M Mini FEC and LAN743x)
 - 1x MicroSD connector
 - 1x USB 2.0 Front Panel connector
 - 1x SPI connector
 - 1x Serial connector supporting 2x-UART or 1x-UART configured as 1 of:
   RS232 w/ flow-control, RS485, RS422
 - PCIe Clock generator
 - GPS and accelerometer
 - Media Expansion connector (MIPI-CSI/MIPI-DSI/GPIO/I2S)
 - I/O connector with 2x-ADC,2x-GPIO,1x-UART,1x-I2C
 - wide range power supply

The GW73xx Baseboard contains:
 - 3x MiniPCIe Socket with USB2.0, PCIe, and SIM
 - 2x RJ45 GbE (i.MX 8M Mini FEC and LAN743x)
 - 1x MicroSD connector
 - 1x USB 2.0 Front Panel connector
 - 1x SPI connector
 - 1x Serial connector supporting 2x-UART or 1x-UART configured as 1 of:
   RS232 w/ flow-control, RS485, RS422
 - WiFi/BT
 - PCIe Clock generator
 - GPS and accelerometer
 - Media Expansion connector (MIPI-CSI/MIPI-DSI/GPIO/I2S)
 - I/O connector with 2x-ADC,2x-GPIO,1x-UART,1x-I2C
 - wide range power supply

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