staging: comedi: das1800: remove 'ao_ability' boardinfo

The "da" and "hc" type boards have normal analog outputs. The
"ao" type boards have move advanced analog outputs with waveform
generation capability.

Remove the 'ao_ability' member of the boardinfo and use the
'id' member to determine if the subdevice should be initialized.

The "ao" waveform analog outputs are not currently supported.
For aesthetics, add an else if for the initialization of the
subdevice for these boards.

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>