mac80211: add mt7601u driver

firmware is not available in linux-firmware yet
so use official driver source

Signed-off-by: Dirk Neukirchen <dirkneukirchen@web.de>


git-svn-id: svn://svn.openwrt.org/openwrt/trunk@46682 3c298f89-4303-0410-b956-a3cf2f4a3e73