ipv6: use seq_release_private for ip6mr.c /proc entries

In ip6mr.c, /proc entries /proc/net/ip6_mr_cache and /proc/net/ip6_mr_vif
are opened with seq_open_private(), thus seq_release_private() should be 
used to release them.
Should fix a small memory leak.
Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6mr.c

@@ -224,7 +224,7 @@ static struct file_operations ip6mr_vif_fops = {
 	.open    = ip6mr_vif_open,
 	.read    = seq_read,
 	.llseek  = seq_lseek,
-	.release = seq_release,
+	.release = seq_release_private,
 };
 
 static void *ipmr_mfc_seq_start(struct seq_file *seq, loff_t *pos)
@@ -338,7 +338,7 @@ static struct file_operations ip6mr_mfc_fops = {
 	.open    = ipmr_mfc_open,
 	.read    = seq_read,
 	.llseek  = seq_lseek,
-	.release = seq_release,
+	.release = seq_release_private,
 };
 #endif