staging: comedi: gsc_hpdi: rename 'plx9080_iobase' in private data

Rename this member to fix two checkpatch.pl warnings about lines > 80
characters.

Also remove the unnecessary comment.

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>