Revert Staging: at76_usb: update drivers/staging/at76_usb w/ mac80211 port

Reverts 02227c28
(Had to be done by hand due to other patches that had come after this.)

Turns out that we don't want the mac80211 port of this driver just yet, as
there is a different driver working on adding this support.

So keep things old and different for now.

This is being reverted at the request of the linux-wireless developers.

Cc: Kalle Valo <kalle.valo@iki.fi>
Cc: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>