iwlwifi: set correct AC to swq_id for aggregation

When starting an aggregation session, the swq_id is generated in function
iwl_virtual_agg_queue_num() where the first parameter is supposed to be
the Access Class, but it used the tx fifo ID instead. This means the AC
value stored in swq_id is incorrect. To test this, look at the tx_queue
file in debugfs while transmitting Best Effort flow (ac=2), it shows:
hwq 10: read=0 write=0 stop=0 swq_id=0xa9 (ac 1/hwq 10)
After this fix, it will show:
hwq 10: read=0 write=0 stop=0 swq_id=0xaa (ac 2/hwq 10)
Signed-off-by: Shanyu Zhao <shanyu.zhao@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>

drivers/net/wireless/iwlwifi/iwl-agn-tx.c

@@ -83,6 +83,15 @@ static inline int get_fifo_from_ac(u8 ac)
 	return ac_to_fifo[ac];
 }
 
+static inline int get_ac_from_tid(u16 tid)
+{
+	if (likely(tid < ARRAY_SIZE(tid_to_ac)))
+		return tid_to_ac[tid];
+
+	/* no support for TIDs 8-15 yet */
+	return -EINVAL;
+}
+
 static inline int get_fifo_from_tid(u16 tid)
 {
 	if (likely(tid < ARRAY_SIZE(tid_to_ac)))
@@ -991,7 +1000,7 @@ int iwlagn_tx_agg_start(struct iwl_priv *priv, const u8 *ra, u16 tid, u16 *ssn)
 	tid_data = &priv->stations[sta_id].tid[tid];
 	*ssn = SEQ_TO_SN(tid_data->seq_number);
 	tid_data->agg.txq_id = txq_id;
-	priv->txq[txq_id].swq_id = iwl_virtual_agg_queue_num(tx_fifo, txq_id);
+	priv->txq[txq_id].swq_id = iwl_virtual_agg_queue_num(get_ac_from_tid(tid), txq_id);
 	spin_unlock_irqrestore(&priv->sta_lock, flags);
 
 	ret = priv->cfg->ops->lib->txq_agg_enable(priv, txq_id, tx_fifo,