staging: comedi: cb_pcidas: remove NUM_CHANNELS_* defines

These defines don't add any additional clarity to the driver. Just
remove them.

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>