Bluetooth: Use locked l2cap_state_change()

No one was protecting the state set in l2cap_send_disconn_req()
Acked-by: NMarcel Holtmann <marcel@holtmann.org>
Signed-off-by: NGustavo Padovan <gustavo.padovan@collabora.co.uk>

net/bluetooth/l2cap_core.c

@@ -1062,7 +1062,7 @@ static void l2cap_send_disconn_req(struct l2cap_conn *conn,
 	}
 
 	if (chan->chan_type == L2CAP_CHAN_CONN_FIX_A2MP) {
-		__l2cap_state_change(chan, BT_DISCONN);
+		l2cap_state_change(chan, BT_DISCONN);
 		return;
 	}