staging: comedi: skel: use comedi_dio_update_state()

Convert this driver to use the comedi_dio_update_state() helper
function.

Tidy up the comments to reflect the new code.

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>