wl12xx: fix race condition during recovery in AP mode

When operating as AP, the TX queues are not stopped when we start
recovery. mac80211 is notified only after the fact. When there is
pending TX, it will be queued even after the FW is down. This leads to
situations where the TX queues are stopped (because of the TX-watermark
mechanism), and are never woken up when we return from recovery.

Fix this by explicitly stopping the TX queues when before initiating
recovery.

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>