mac80211: allocate only one RX queue

We don't have multiple RX queues, so there's no use
in allocating multiple, use alloc_netdev_mqs() to
allocate multiple TX but only one RX queue.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>