Bluetooth: Fix possible missing I-Frame acknowledgement

Make l2cap_ertm_send return number of pending I-Frames transmitted
instead of all (pending + retransmitted) I-Frames transmitted.

As only pending I-Frames are considered as acknowledgement, this could
lead to situation when no ACK was sent in __l2cap_send_ack (if only
already transmitted I-Frames were retransmitted).

Signed-off-by: Szymon Janc <szymon.janc@tieto.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Acked-by: Gustavo F. Padovan <padovan@profusion.mobi>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>

net/bluetooth/l2cap_core.c

@@ -1453,17 +1453,17 @@ static int l2cap_ertm_send(struct l2cap_chan *chan)
 
 		chan->next_tx_seq = __next_seq(chan, chan->next_tx_seq);
 
-		if (bt_cb(skb)->retries == 1)
+		if (bt_cb(skb)->retries == 1) {
 			chan->unacked_frames++;
+			nsent++;
+		}
 
 		chan->frames_sent++;
 
 		if (skb_queue_is_last(&chan->tx_q, skb))
 			chan->tx_send_head = NULL;
 		else
 			chan->tx_send_head = skb_queue_next(&chan->tx_q, skb);
-
-		nsent++;
 	}
 
 	return nsent;