staging: comedi: pcl724: tidy up pcl724_attach()

Consolidate the special handling of the 'hoard->can_have96' flag.
This flag overrides the iorange and n_subdevices for the PCL-724
board when it is used in a 96 DIO configuration.

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