staging: comedi: ni_daq_700: update driver comment

Reformat the comment describing this comedi driver to use the usual
block comment format.

Also remove reference to digital I/O emulating an 8255, because it
doesn't, and remove "DIO only" from the "Description:" line as it also
supports analog inputs.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>