ARM: dts: imx6qdl-wandboard: Add usbotg support

Tested via g_ether:

$ modprobe g_ether
using random self ethernet address
using random host ethernet address
usb0: HOST MAC 42:b5:26:a9:48:21
usb0: MAC 36:a6:85:9b:9e:13
using random self ethernet address
using random host ethernet address
g_ether gadget: Ethernet Gadget, version: Memorial Day 2008
g_ether gadget: g_ether ready
$ g_ether gadget: high-speed config #1: CDC Ethernet (ECM)
$ ifconfig usb0 10.0.0.2

Then on the PC host side:

~$ sudo ifconfig usb0 10.0.0.1
~$ ping 10.0.0.2
PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.
64 bytes from 10.0.0.2: icmp_req=1 ttl=64 time=1.26 ms
64 bytes from 10.0.0.2: icmp_req=2 ttl=64 time=0.280 ms
64 bytes from 10.0.0.2: icmp_req=3 ttl=64 time=0.297 ms

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>