AA: mac80211: merge ath9k fixes from bb

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/branches/attitude_adjustment@42647 3c298f89-4303-0410-b956-a3cf2f4a3e73
AA: ar71xx: add support for TP-LINK TL-WR847N v8 (variant of TL-WR841N v8)