ath9k: merge a fix for queue start/stop handling (fixes #18164, #18130)

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

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@43011 3c298f89-4303-0410-b956-a3cf2f4a3e73