staging: comedi: addi_apci_16xx: cleanup subdevice initialization

The comedi subdevice in this driver is a simple digital i/o
device.

Currently, the code abuses the comedi API by redefining the
COMEDI_SUBD_SERIAL type as COMEDI_SUBD_TTLIO and using that
for the 's->type'. Remove the defines and use the proper type,
COMEDI_SUBD_DIO.

The current code also sets the subdev_flags SDF_GROUND and SDF_COMMON
for the subdevice. These flags really only have meaning for analog
subdevices. Remove them.

All the boards supported by this driver use the same functions for
the subdevice 'insn_*' operations. Remove this information from
the boardinfo and set the s->insn_* operations directly in the init.

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>