mac80211: use offchannel queue only when supported

Commit 3a25a8c8 ("mac80211: add improved HW queue control")
added support for offchannel queue mapping. However, this
mapping is only valid when the driver supports
IEEE80211_HW_QUEUE_CONTROL.

Check whether the driver supports IEEE80211_HW_QUEUE_CONTROL
before setting the hw_queue to the mapped offchannel queue.

(This patch doesn't have any actual effect, because
hw_queue is overridden in ieee80211_tx() anyway,
so this is merely some cleanup)
Signed-off-by: Eliad Peller <eliad@wizery.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/cfg.c

@@ -2304,7 +2304,8 @@ static int ieee80211_mgmt_tx(struct wiphy *wiphy, struct net_device *dev,
 
 	IEEE80211_SKB_CB(skb)->flags = flags;
 
-	if (flags & IEEE80211_TX_CTL_TX_OFFCHAN)
+	if (local->hw.flags & IEEE80211_HW_QUEUE_CONTROL &&
+	    flags & IEEE80211_TX_CTL_TX_OFFCHAN)
 		IEEE80211_SKB_CB(skb)->hw_queue =
 			local->hw.offchannel_tx_hw_queue;
 
@@ -2349,6 +2350,7 @@ static int ieee80211_mgmt_tx(struct wiphy *wiphy, struct net_device *dev,
 		/* modify cookie to prevent API mismatches */
 		*cookie ^= 2;
 		IEEE80211_SKB_CB(skb)->flags |= IEEE80211_TX_CTL_TX_OFFCHAN;
+		if (local->hw.flags & IEEE80211_HW_QUEUE_CONTROL)
 			IEEE80211_SKB_CB(skb)->hw_queue =
 				local->hw.offchannel_tx_hw_queue;
 		local->hw_roc_skb = skb;