net_sched: cls_flow: add key rxhash

We can use rxhash to classify the traffic into flows. As rxhash maybe
supplied by NIC or RPS, it is cheaper.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Acked-by: Jamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/pkt_cls.h

@@ -332,6 +332,7 @@ enum {
 	FLOW_KEY_SKUID,
 	FLOW_KEY_SKGID,
 	FLOW_KEY_VLAN_TAG,
+	FLOW_KEY_RXHASH,
 	__FLOW_KEY_MAX,
 };