staging: dgnc: changes arguments in sizeof

The arguments that were passed into sizeof were
generic. This patch changes this by putting
the actual item that we need a size of instead.

For example:
-   kzalloc(sizeof(struct dgnc_board), GFP_KERNEL);
+   kzalloc(sizeof(*brd), GFP_KERNEL);

Signed-off-by: Lidza Louina <lidza.louina@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>