USB: quatech2: fix memory leak in error path

Fix memory leak in attach error path where the read urb was never freed.

Cc: Bill Pemberton <wfp5p@virginia.edu>
Cc: <stable@vger.kernel.org>
Signed-off-by: NJohan Hovold <jhovold@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/quatech2.c

@@ -823,6 +823,7 @@ static int qt2_setup_urbs(struct usb_serial *serial)
 	if (status != 0) {
 		dev_err(&serial->dev->dev,
 			"%s - submit read urb failed %i\n", __func__, status);
+		usb_free_urb(serial_priv->read_urb);
 		return status;
 	}