[Bluetooth]: Call tty_hangup() when DCD is de-asserted

The RFCOMM layer does not handle properly the de-assertation
of CD signal. It should call tty_hangup() to work properly.
Signed-off-by: Timo Ters <ext-timo.teras@nokia.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bluetooth/rfcomm/tty.c

@@ -531,6 +531,11 @@ static void rfcomm_dev_modem_status(struct rfcomm_dlc *dlc, u8 v24_sig)
 
 	BT_DBG("dlc %p dev %p v24_sig 0x%02x", dlc, dev, v24_sig);
 
+	if ((dev->modem_status & TIOCM_CD) && !(v24_sig & RFCOMM_V24_DV)) {
+		if (dev->tty && !C_CLOCAL(dev->tty))
+			tty_hangup(dev->tty);
+	}
+
 	dev->modem_status = 
 		((v24_sig & RFCOMM_V24_RTC) ? (TIOCM_DSR | TIOCM_DTR) : 0) |
 		((v24_sig & RFCOMM_V24_RTR) ? (TIOCM_RTS | TIOCM_CTS) : 0) |