staging: comedi: das1800: remove the private data member comments

The comments about the members of the private data are not really
necessary and removing them fixes a couple checkpatch.pl issues.

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>