drbd: use proc_create_data with explicit NULL argument

To document that we know about deprecation of proc_create,
even though we are not affected, as we don't use the ->data member,
open code proc_create_data(..., NULL);

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
1 file changed