ARM: dts: imx: add Gateworks Ventana GW5903 support

The Gateworks Ventana GW5903 is a single-board computer based on the NXP
IMX6 SoC with the following features:
 * IMX6 DualLite Soc (supports IMX6S,IMX6DL,IMX6Q)
 * 4GiB DDR3 DRAM
 * 32GB eMMC
 * 1x microSD connector
 * Gateworks System Controller:
  - hardware watchdog
  - hardware monitor
  - pushbutton controller
  - EEPROM storage
  - power control
 * JTAG programmable
 * Inertial Module
 * uBlox EMMY-W1 (bluetooth/nfc/802.11ac)

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