staging: comedi: pcmuio: tidy up driver #define's

Add some whitespace to the #defines to make them more readable.
Tidy up the comments.

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>