staging: comedi: contec_pci_dio: define register map for board

Only one board type is supported by this driver. Instead of
passing the register offsets for the digital in/out ports in
the boardinfo, define the register map and use that to access
the ports.

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>