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: Luciano Coelho <coelho@ti.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 6e85fae..23d1da3 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -163,7 +163,8 @@
 			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;
 	}