staging: comedi: cb_pcimdda: remove dio_offset from the boardinfo

The 8255 device is located at a fixed offset from the base
address of the card. There is not need to carry this offset
in the boardinfo. Remove 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>