[Bluetooth] Disconnect L2CAP connection after last RFCOMM DLC

The RFCOMM specification says that the device closing the last DLC on
a particular session is responsible for closing the multiplexer by
closing the corresponding L2CAP channel.
Signed-off-by: NVille Tervo <ville.tervo@nokia.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

net/bluetooth/rfcomm/core.c

@@ -1058,6 +1058,12 @@ static int rfcomm_recv_ua(struct rfcomm_session *s, u8 dlci)
 		case BT_DISCONN:
 			d->state = BT_CLOSED;
 			__rfcomm_dlc_close(d, 0);
+
+			if (list_empty(&s->dlcs)) {
+				s->state = BT_DISCONN;
+				rfcomm_send_disc(s, 0);
+			}
+
 			break;
 		}
 	} else {
@@ -1067,6 +1073,10 @@ static int rfcomm_recv_ua(struct rfcomm_session *s, u8 dlci)
 			s->state = BT_CONNECTED;
 			rfcomm_process_connect(s);
 			break;
+
+		case BT_DISCONN:
+			rfcomm_session_put(s);
+			break;
 		}
 	}
 	return 0;