[ATALK/DECNET]: Use seq_open_private in appletalk and decnet.

These two also perform manual seq_open_private, so patch them both at
once. But unlike ATM code, these already use the seq_release_private,
so I splitted this patch from the previous one.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/decnet/af_decnet.c b/net/decnet/af_decnet.c
index acd48ee..23fd95a 100644
--- a/net/decnet/af_decnet.c
+++ b/net/decnet/af_decnet.c
@@ -2320,25 +2320,8 @@
 
 static int dn_socket_seq_open(struct inode *inode, struct file *file)
 {
-	struct seq_file *seq;
-	int rc = -ENOMEM;
-	struct dn_iter_state *s = kmalloc(sizeof(*s), GFP_KERNEL);
-
-	if (!s)
-		goto out;
-
-	rc = seq_open(file, &dn_socket_seq_ops);
-	if (rc)
-		goto out_kfree;
-
-	seq		= file->private_data;
-	seq->private	= s;
-	memset(s, 0, sizeof(*s));
-out:
-	return rc;
-out_kfree:
-	kfree(s);
-	goto out;
+	return seq_open_private(file, &dn_socket_seq_ops,
+			sizeof(struct dn_iter_state));
 }
 
 static const struct file_operations dn_socket_seq_fops = {