netfilter: ip6t_SYNPROXY: unnecessary to check whether ip6_route_output returns NULL

ip6_route_output() will never return a NULL pointer, so there's no need
to check it.
Signed-off-by: Liping Zhang <liping.zhang@spreadtrum.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/ipv6/netfilter/ip6t_SYNPROXY.c

@@ -60,7 +60,7 @@ synproxy_send_tcp(struct net *net,
 	fl6.fl6_dport = nth->dest;
 	security_skb_classify_flow((struct sk_buff *)skb, flowi6_to_flowi(&fl6));
 	dst = ip6_route_output(net, NULL, &fl6);
-	if (dst == NULL || dst->error) {
+	if (dst->error) {
 		dst_release(dst);
 		goto free_nskb;
 	}