staging: dgnc: fix checkpatch.pl usage of volatile.

This is a patch to the dgnc_cls.c file that fixes up volatile usage
warning found by the checkpatch.pl tool

Signed-off-by: S. Stalin Srinivasan <stalinsrinivasan.s@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>