The driver relies on the generic write implementation but did not call
generic close.
Note that the call to kill the read urb is not redundant, as mct_u232
uses an interrupt urb from the second port as the read urb and that
generic close therefore fails to kill it.
Compile-only tested.
Cc: <stable@vger.kernel.org> Signed-off-by: Johan Hovold <jhovold@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>