Bluetooth: Optimize SREJ_QUEUE append

When the I-frame received is the expected, i.e., its tx_seq is equal to
expected_tx_seq and we are under a SREJ, we can just add it to the tail
of the list. Doing that we change the complexity from O(n) to O(1).
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Reviewed-by: João Paulo Rechi Vita <jprvita@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/l2cap.c

@@ -3542,7 +3542,9 @@ static inline int l2cap_data_channel_iframe(struct sock *sk, u16 rx_control, str
 	pi->expected_tx_seq = (pi->expected_tx_seq + 1) % 64;
 
 	if (pi->conn_state & L2CAP_CONN_SREJ_SENT) {
-		l2cap_add_to_srej_queue(sk, skb, tx_seq, sar);
+		bt_cb(skb)->tx_seq = tx_seq;
+		bt_cb(skb)->sar = sar;
+		__skb_queue_tail(SREJ_QUEUE(sk), skb);
 		return 0;
 	}