rtnetlink: ipv6: convert remaining users to rtnl_register_module

convert remaining users of rtnl_register to rtnl_register_module
and un-export rtnl_register.

Requested-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index a5ad842..ed06b11 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -6627,7 +6627,9 @@ int __init addrconf_init(void)
 				   RTNL_FLAG_DOIT_UNLOCKED);
 	if (err < 0)
 		goto errout;
-	ipv6_addr_label_rtnl_register();
+	err = ipv6_addr_label_rtnl_register();
+	if (err < 0)
+		goto errout;
 
 	return 0;
 errout: