gro: refetch inet6_protos[] after pulling ext headers

ipv6_gro_receive() doesn't update the protocol ops after pulling
the ext headers. It looks like a typo.
Signed-off-by: NZheng Yan <zheng.z.yan@intel.com>
Acked-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/af_inet6.c

@@ -875,6 +875,7 @@ static struct sk_buff **ipv6_gro_receive(struct sk_buff **head,
 		skb_reset_transport_header(skb);
 		__skb_push(skb, skb_gro_offset(skb));
 
+		ops = rcu_dereference(inet6_protos[proto]);
 		if (!ops || !ops->gro_receive)
 			goto out_unlock;