wifi: rt2x00: Fix "Error - Attempt to send packet over invalid queue 2"

Even though ieee80211_hw.queues is set to 2, the ralink rt2x00 driver
is seeing tx skbs submitted to it with the queue-id set to 2 / set to
IEEE80211_AC_BE on a rt2500 card when associating with an access-point.

This causes rt2x00queue_get_tx_queue() to return NULL and the following
error to be logged: "ieee80211 phy0: rt2x00mac_tx: Error - Attempt to
send packet over invalid queue 2", after which association with the AP
fails.

This patch works around this by mapping QID_AC_BE and QID_AC_BK
to QID_AC_VI when there are only 2 tx_queues.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
The net/mac80211 code has checks for local->hw.queues < IEEE80211_NUM_ACS
in various places and returns queue-id 0 when this condition is true.

So it looks like the rt2x00 driver receiving a queue-id of 2 /
IEEE80211_AC_BE might actually be a bug in the mac80211 core code,
I will send out a separate email about this.

drivers/net/wireless/ralink/rt2x00/rt2x00.h

@@ -1309,8 +1309,11 @@ void rt2x00queue_unmap_skb(struct queue_entry *entry);
  */
 static inline struct data_queue *
 rt2x00queue_get_tx_queue(struct rt2x00_dev *rt2x00dev,
-			 const enum data_queue_qid queue)
+			 enum data_queue_qid queue)
 {
+	if (queue >= rt2x00dev->ops->tx_queues && queue < IEEE80211_NUM_ACS)
+		queue = rt2x00dev->ops->tx_queues - 1;
+
 	if (queue < rt2x00dev->ops->tx_queues && rt2x00dev->tx)
 		return &rt2x00dev->tx[queue];