USB: fix interaction between different interfaces in an "Option" usb …

…device

Just the serial port in the first interface should control DTR and RTS
lines. This way, the closing of the rest of the ports does not produce a=
hangup in the communication.

Signed-off-by: Miguel Angel Alvarez <ma.alvarez@ziv.es>
Signed-off-by: Matthias Urlichs <matthias@urlichs.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/option.c

@@ -625,6 +625,9 @@ static int option_send_setup(struct usb_serial_port *port)
 
 	dbg("%s", __FUNCTION__);
 
+	if (port->number != 0)
+		return 0;
+
 	portdata = usb_get_serial_port_data(port);
 
 	if (port->tty) {