staging: comedi: cb_pcimdda: remove dio_chans from the private data

The cards supported by this driver always have 8255 compatible
device. Remove the dio_chans variable from the private data and
always initialize the 8255 subdevice.

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>