staging: comedi: cb_pcidda: remove code in #if 0/#endif blocks

The functions cb_pcidda_ai_cmd(), cb_pcidda_ai_cmdtest(), and
cb_pcidda_ns_to_timer() are all partially coded stubs for command
support with the analog output subdevice. Just remove the code
since it is #if 0'ed out. It can be added back later if command
support is completed.

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>