[IPSEC]: Get nexthdr from caller in xfrm6_rcv_spi

Currently xfrm6_rcv_spi gets the nexthdr value itself from the packet.
This means that we need to fix up the value in case we have a 4-on-6
tunnel.  Moving this logic into the caller simplifies things and allows
us to merge the code with IPv4.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/xfrm6_tunnel.c b/net/ipv6/xfrm6_tunnel.c
index 6c67ac1..fae90ff 100644
--- a/net/ipv6/xfrm6_tunnel.c
+++ b/net/ipv6/xfrm6_tunnel.c
@@ -257,7 +257,7 @@
 	__be32 spi;
 
 	spi = xfrm6_tunnel_spi_lookup((xfrm_address_t *)&iph->saddr);
-	return xfrm6_rcv_spi(skb, spi) > 0 ? : 0;
+	return xfrm6_rcv_spi(skb, IPPROTO_IPV6, spi) > 0 ? : 0;
 }
 
 static int xfrm6_tunnel_err(struct sk_buff *skb, struct inet6_skb_parm *opt,