[IPV6]: Decentralize EXPORT_SYMBOLs.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 121f31c..886c5be 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -319,6 +319,8 @@
 	return -EINVAL;
 }
 
+EXPORT_SYMBOL(ndisc_mc_map);
+
 static u32 ndisc_hash(const void *pkey, const struct net_device *dev)
 {
 	const u32 *p32 = pkey;