[NET] NETNS: Omit seq_net_private->net without CONFIG_NET_NS.

Without CONFIG_NET_NS, no namespace other than &init_net exists,
no need to store net in seq_net_private.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 712a7bf..1d16d95 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1758,7 +1758,7 @@
 
 		for (j = 0; j <= hash->mask; j++) {
 			sk_for_each(s, node, &hash->table[j]) {
-				if (sock_net(s) != iter->p.net)
+				if (sock_net(s) != seq_file_net(seq))
 					continue;
 				if (off == pos) {
 					iter->link = i;
@@ -1794,7 +1794,7 @@
 	s = v;
 	do {
 		s = sk_next(s);
-	} while (s && (sock_net(s) != iter->p.net));
+	} while (s && sock_net(s) != seq_file_net(seq));
 	if (s)
 		return s;
 
@@ -1806,7 +1806,7 @@
 
 		for (; j <= hash->mask; j++) {
 			s = sk_head(&hash->table[j]);
-			while (s && sock_net(s) != iter->p.net)
+			while (s && sock_net(s) != seq_file_net(seq))
 				s = sk_next(s);
 			if (s) {
 				iter->link = i;