ar9170usb: add vendor and device ID for Qwest/Actiontec 802AIN Wireless N USB Network Adapter

* add support for the Qwest/Actiontec 802AIN Wireless N USB Network Adapter.

lsusb identifies the device as: "ID 1668:1200 Actiontec Electronics, Inc. [hex]"

usb_modeswitch package and appropriate rules are required to switch
the device from "ID 0ace:20ff ZyDas"

Changes-licensed-under: GPL
Signed-off-by: Steve Tanner <steve.tanner@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>