Bluetooth: shell: Add sent callback to L2CAP ops

This prints to the output when a packet finishes transmitting:

uart:~$ l2cap send 2
Outgoing data channel 0x005166a0 transmitted
Outgoing data channel 0x005166a0 transmitted

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

subsys/bluetooth/shell/l2cap.c

@@ -116,6 +116,11 @@ static int l2cap_recv(struct bt_l2cap_chan *chan, struct net_buf *buf)
 	return 0;
 }
 
+static void l2cap_sent(struct bt_l2cap_chan *chan)
+{
+	shell_print(ctx_shell, "Outgoing data channel %p transmitted", chan);
+}
+
 static void l2cap_connected(struct bt_l2cap_chan *chan)
 {
 	struct l2ch *c = L2CH_CHAN(chan);
@@ -143,6 +148,7 @@ static struct net_buf *l2cap_alloc_buf(struct bt_l2cap_chan *chan)
 static struct bt_l2cap_chan_ops l2cap_ops = {
 	.alloc_buf	= l2cap_alloc_buf,
 	.recv		= l2cap_recv,
+	.sent		= l2cap_sent,
 	.connected	= l2cap_connected,
 	.disconnected	= l2cap_disconnected,
 };