[NETFILTER]: nfnetlink_log: iterator functions need iter_state * only

get_*() don't need access to seq_file - iter_state is enough for them.

Signed-off-by: Michal Miroslaw <mirq-linux@rere.qmqm.pl>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>