at76c50x-usb: add driver

This is a driver for usb devices based on at76c50x chipset. This is
a mac80211 port of the original at76_usb driver.

Signed-off-by: Kalle Valo <kalle.valo@iki.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
4 files changed