mac80211: check IEEE80211_HW_QUEUE_CONTROL in ieee80211_check_queues()

Commit 3a25a8c8 (mac80211: add improved HW queue control) introduced a
bug when running in AP mode without the IEEE80211_HW_QUEUE_CONTROL
flag set.  The ieee80211_check_queues() function always returns
-EINVAL, preventing AP mode from starting.  To fix this, check whether
this flag is set before checking if cab_queue is set properly.
Signed-off-by: NLuciano Coelho <coelho@ti.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

net/mac80211/iface.c

@@ -163,7 +163,8 @@ static int ieee80211_check_queues(struct ieee80211_sub_if_data *sdata)
 			return -EINVAL;
 	}
 
-	if (sdata->vif.type != NL80211_IFTYPE_AP) {
+	if ((sdata->vif.type != NL80211_IFTYPE_AP) ||
+	    !(sdata->local->hw.flags & IEEE80211_HW_QUEUE_CONTROL)) {
 		sdata->vif.cab_queue = IEEE80211_INVAL_HW_QUEUE;
 		return 0;
 	}