[NEIGH]: Make /proc/net/arp opening consistent with seq_net_open semantics

seq_open_net requires that first field of the seq->private data to be
struct seq_net_private. In reality this is a single pointer to a
struct net for now. The patch makes code consistent.
Signed-off-by: NDenis V. Lunev <den@openvz.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/neighbour.h

@@ -223,7 +223,7 @@ extern void __neigh_for_each_release(struct neigh_table *tbl, int (*cb)(struct n
 extern void pneigh_for_each(struct neigh_table *tbl, void (*cb)(struct pneigh_entry *));
 
 struct neigh_seq_state {
-	struct net *net;
+	struct seq_net_private p;
 	struct neigh_table *tbl;
 	void *(*neigh_sub_iter)(struct neigh_seq_state *state,
 				struct neighbour *n, loff_t *pos);

net/core/neighbour.c

@@ -2142,7 +2142,7 @@ EXPORT_SYMBOL(__neigh_for_each_release);
 static struct neighbour *neigh_get_first(struct seq_file *seq)
 {
 	struct neigh_seq_state *state = seq->private;
-	struct net *net = state->net;
+	struct net *net = state->p.net;
 	struct neigh_table *tbl = state->tbl;
 	struct neighbour *n = NULL;
 	int bucket = state->bucket;
@@ -2183,7 +2183,7 @@ static struct neighbour *neigh_get_next(struct seq_file *seq,
 					loff_t *pos)
 {
 	struct neigh_seq_state *state = seq->private;
-	struct net *net = state->net;
+	struct net *net = state->p.net;
 	struct neigh_table *tbl = state->tbl;
 
 	if (state->neigh_sub_iter) {
@@ -2243,7 +2243,7 @@ static struct neighbour *neigh_get_idx(struct seq_file *seq, loff_t *pos)
 static struct pneigh_entry *pneigh_get_first(struct seq_file *seq)
 {
 	struct neigh_seq_state *state = seq->private;
-	struct net * net = state->net;
+	struct net * net = state->p.net;
 	struct neigh_table *tbl = state->tbl;
 	struct pneigh_entry *pn = NULL;
 	int bucket = state->bucket;
@@ -2266,7 +2266,7 @@ static struct pneigh_entry *pneigh_get_next(struct seq_file *seq,
 					    loff_t *pos)
 {
 	struct neigh_seq_state *state = seq->private;
-	struct net * net = state->net;
+	struct net * net = state->p.net;
 	struct neigh_table *tbl = state->tbl;
 
 	pn = pn->next;