Bluetooth: A2MP: Do not reference hci_conn

Make A2MP channel special channel which do not reference hci_conn.
This prevents from keeping ACL connection open when all L2CAP
channels got closed.

hci_conn_hold and hci_conn_put are not reference counts on the
hci_conn structure in the typical way.  They are reference counts for
the ACL.  When you do the last hci_conn_put, the ACL is disconnected
after a timeout.
Reported-by: Mat Martineau <mathewm@codeaurora.org>
Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

net/bluetooth/a2mp.c

@@ -481,8 +481,6 @@ static struct l2cap_chan *a2mp_chan_open(struct l2cap_conn *conn)
 
 	BT_DBG("chan %p", chan);
 
-	hci_conn_hold(conn->hcon);
-
 	chan->chan_type = L2CAP_CHAN_CONN_FIX_A2MP;
 	chan->flush_to = L2CAP_DEFAULT_FLUSH_TO;
 

net/bluetooth/l2cap_core.c

@@ -514,7 +514,9 @@ void l2cap_chan_del(struct l2cap_chan *chan, int err)
 		l2cap_chan_put(chan);
 
 		chan->conn = NULL;
-		hci_conn_put(conn->hcon);
+
+		if (chan->chan_type != L2CAP_CHAN_CONN_FIX_A2MP)
+			hci_conn_put(conn->hcon);
 	}
 
 	if (chan->ops->teardown)