staging: comedi: cb_pcimdda: remove the DIO_METHODS

The digital i/o on this card is handled by an 8255 compatible
device. There are not other options. Remove the DIO_METHODS
enum as well as the dio_method variable in the boardinfo and
the code dealing with it.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>