nf_defrag_ipv6: fix oops on module unloading

fix copy-paste error introduced in linux-next commit
"ipv6: add a new namespace for nf_conntrack_reasm"
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Amerigo Wang <amwang@redhat.com>
Cc: David S. Miller <davem@davemloft.net>
Acked-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/netfilter/nf_conntrack_reasm.c

@@ -106,7 +106,7 @@ static int __net_init nf_ct_frag6_sysctl_register(struct net *net)
 	if (hdr == NULL)
 		goto err_reg;
 
-	net->ipv6.sysctl.frags_hdr = hdr;
+	net->nf_frag.sysctl.frags_hdr = hdr;
 	return 0;
 
 err_reg: