USB: serial: opticon: fix CTS retrieval at open

The opticon driver used a control request at open to trigger a CTS
status notification to be sent over the bulk-in pipe. When the driver
was converted to using the generic read implementation, an inverted test
prevented this request from being sent, something which could lead to
TIOCMGET reporting an incorrect CTS state.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 7a6ee2b02751 ("USB: opticon: switch to generic read
implementation")
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/opticon.c

@@ -142,7 +142,7 @@ static int opticon_open(struct tty_struct *tty, struct usb_serial_port *port)
 	usb_clear_halt(port->serial->dev, port->read_urb->pipe);
 
 	res = usb_serial_generic_open(tty, port);
-	if (!res)
+	if (res)
 		return res;
 
 	/* Request CTS line state, sometimes during opening the current