net: Add utility function to copy skb hash

Adds skb_copy_hash to copy rxhash and l4_rxhash from one skb to another.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 06e72d3..2b6b863 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -712,9 +712,8 @@
 	new->inner_network_header = old->inner_network_header;
 	new->inner_mac_header = old->inner_mac_header;
 	skb_dst_copy(new, old);
-	new->rxhash		= old->rxhash;
+	skb_copy_hash(new, old);
 	new->ooo_okay		= old->ooo_okay;
-	new->l4_rxhash		= old->l4_rxhash;
 	new->no_fcs		= old->no_fcs;
 	new->encapsulation	= old->encapsulation;
 #ifdef CONFIG_XFRM