netfilter: Use correct return for seq_show functions

Using seq_has_overflowed doesn't produce the right return value.
Either 0 or -1 is, but 0 is much more common and works well when
seq allocation retries.

I believe this doesn't matter as the initial allocation is always
sufficient, this is just a correctness patch.

Miscellanea:

o Don't use strlen, use *ptr to determine if a string
  should be emitted like all the other tests here
o Delete unnecessary return statements
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nfnetlink_queue_core.c

@@ -1257,7 +1257,7 @@ static int seq_show(struct seq_file *s, void *v)
 		   inst->copy_mode, inst->copy_range,
 		   inst->queue_dropped, inst->queue_user_dropped,
 		   inst->id_sequence, 1);
-	return seq_has_overflowed(s);
+	return 0;
 }
 
 static const struct seq_operations nfqnl_seq_ops = {

net/netfilter/x_tables.c

@@ -947,10 +947,8 @@ static int xt_table_seq_show(struct seq_file *seq, void *v)
 {
 	struct xt_table *table = list_entry(v, struct xt_table, list);
 
-	if (strlen(table->name)) {
+	if (*table->name)
 		seq_printf(seq, "%s\n", table->name);
-		return seq_has_overflowed(seq);
-	} else
 	return 0;
 }
 
@@ -1087,10 +1085,8 @@ static int xt_match_seq_show(struct seq_file *seq, void *v)
 		if (trav->curr == trav->head)
 			return 0;
 		match = list_entry(trav->curr, struct xt_match, list);
-		if (*match->name == '\0')
-			return 0;
+		if (*match->name)
 			seq_printf(seq, "%s\n", match->name);
-		return seq_has_overflowed(seq);
 	}
 	return 0;
 }
@@ -1142,10 +1138,8 @@ static int xt_target_seq_show(struct seq_file *seq, void *v)
 		if (trav->curr == trav->head)
 			return 0;
 		target = list_entry(trav->curr, struct xt_target, list);
-		if (*target->name == '\0')
-			return 0;
+		if (*target->name)
 			seq_printf(seq, "%s\n", target->name);
-		return seq_has_overflowed(seq);
 	}
 	return 0;
 }