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: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/serial/quatech2.c b/drivers/usb/serial/quatech2.c
index 2cdfdcc..5adb742 100644
--- a/drivers/usb/serial/quatech2.c
+++ b/drivers/usb/serial/quatech2.c
@@ -823,6 +823,7 @@
 	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;
 	}