staging: dgnc: Do not initialise statics to 0 or NULL

This fixes the following checkpatch.pl error:
ERROR: do not initialise statics to 0 or NULL

Signed-off-by: Roberta Dobrescu <roberta.dobrescu@gmail.com>
Acked-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>