imx53: usbarmory: Use ethernet driver model

Enable ethernet driver model as it is mandatory.

Signed-off-by: Andrej Rosano <andrej.rosano@f-secure.com>
diff --git a/configs/usbarmory_defconfig b/configs/usbarmory_defconfig
index f259554..a4cdcca 100644
--- a/configs/usbarmory_defconfig
+++ b/configs/usbarmory_defconfig
@@ -39,3 +39,4 @@
 CONFIG_MXC_UART=y
 CONFIG_USB=y
 CONFIG_USB_EHCI_MX5=y
+CONFIG_DM_ETH=y