pppoe: fix /proc/net/pppoe

If a socket is hashed in last slot of pppoe hash table (PPPOE_HASH_SIZE-1)
we report it many times (up to filling seq buffer)
(Only the last socket of last slot)
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/pppoe.c

@@ -1063,6 +1063,7 @@ static void *pppoe_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 	else {
 		int hash = hash_item(po->pppoe_pa.sid, po->pppoe_pa.remote);
 
+		po = NULL;
 		while (++hash < PPPOE_HASH_SIZE) {
 			po = pn->hash_table[hash];
 			if (po)