imx6: add support for GW53xx

imx6: add support for GW53xx

The Gateworks GW53xx family of products is based on the Freescale
i.MX6DL SoC and offers a small form-factor with peripherals such as:

 * i.MX6DL
 * NAND FLASH
 * 4x PCIe
 * 4x USB EHCI (1x front-panel; 3x PCIe sockets)
 * 1x USB OTG
 * 1x uSD
 * LVDS connector (VLDS for display, PWM/GPIO for backlight, i2c for touch)
 * HDMI Audio/Video out
 * Analog Video in
 * Digital IO
 * Gateworks System Controller
 * Accelerometer
 * Canbus
 * Optional GPS
 * Industrial temp (-40C to +85C)
 * DC input voltage 8 to 42V (Passive PoE and 802.3af)

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39012 3c298f89-4303-0410-b956-a3cf2f4a3e73