openvswitch: Fix key serialization.

Fix typo where mask is used rather than key.

Fixes: 74ed7ab9264("openvswitch: Add support for unique flow IDs.")
Reported-by: Joe Stringer <joestringer@nicira.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Joe Stringer <joestringer@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/openvswitch/flow_netlink.c

@@ -1516,7 +1516,7 @@ int ovs_nla_put_identifier(const struct sw_flow *flow, struct sk_buff *skb)
 /* Called with ovs_mutex or RCU read lock. */
 int ovs_nla_put_masked_key(const struct sw_flow *flow, struct sk_buff *skb)
 {
-	return ovs_nla_put_key(&flow->mask->key, &flow->key,
+	return ovs_nla_put_key(&flow->key, &flow->key,
 				OVS_FLOW_ATTR_KEY, false, skb);
 }