USB: sierra: remove unused variable

Remove unused variable from sierra_release_urb.
Signed-off-by: NJohan Hovold <jhovold@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/sierra.c

@@ -419,9 +419,7 @@ static int sierra_tiocmset(struct tty_struct *tty,
 
 static void sierra_release_urb(struct urb *urb)
 {
-	struct usb_serial_port *port;
 	if (urb) {
-		port = urb->context;
 		kfree(urb->transfer_buffer);
 		usb_free_urb(urb);
 	}