USB: whiteheat: fix broken port configuration

When configuring the port (e.g. set_termios) the port minor number
rather than the port number was used in the request (and they only
coincide for minor number 0).

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