[IPSEC]: Use the correct family for input state lookup

When merging the input paths of IPsec I accidentally left a hard-coded
AF_INET for the state lookup call.  This broke IPv6 obviously.  This
patch fixes by getting the input callers to specify the family through
skb->cb.

Credit goes to Kazunori Miyazawa for diagnosing this and providing an
initial patch.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index ecc02e9..182f10b 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -534,6 +534,7 @@
 	} header;
 
 	unsigned int daddroff;
+	unsigned int family;
 };
 
 #define XFRM_SPI_SKB_CB(__skb) ((struct xfrm_spi_skb_cb *)&((__skb)->cb[0]))