act_nat: the checksum of ICMP doesn't have pseudo header

after updating the value of the ICMP payload, inet_proto_csum_replace4() should
be called with zero pseudohdr.
Signed-off-by: NChangli Gao <xiaosuo@gmail.com>
Acked-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/act_nat.c

@@ -247,7 +247,7 @@ static int tcf_nat(struct sk_buff *skb, struct tc_action *a,
 			iph->saddr = new_addr;
 
 		inet_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr,
-					 1);
+					 0);
 		break;
 	}
 	default: