USB: mos7840: fix urb leak at release

commit 65a4cdbb170e4ec1a7fa0e94936d47e24a17b0e8 upstream.

Make sure control urb is freed at release.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>