also, perhaps installing the kmod-usb-net-rndis package would help?
or kmod-usb-net-cdc-ether depending on which mode the usb dongle is in
http://www.it-slav.net/blogs/2010/07/02/howto-use-rndis-device-in-openwrt-as-a-modem-i-e-htc-desire-with-android/