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 <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv6/ip6mr.c

···
 	.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)
···
 	.open    = ipmr_mfc_open,
 	.read    = seq_read,
 	.llseek  = seq_lseek,
-	.release = seq_release,
+	.release = seq_release_private,
 };
 #endif