flow_offload: include linux/kernel.h from flow_offload.h

flow_stats_update() uses max_t, so ensure we have that defined.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/flow_offload.h b/include/net/flow_offload.h
index a2df99f..36fdb85 100644
--- a/include/net/flow_offload.h
+++ b/include/net/flow_offload.h
@@ -1,6 +1,7 @@
 #ifndef _NET_FLOW_OFFLOAD_H
 #define _NET_FLOW_OFFLOAD_H
 
+#include <linux/kernel.h>
 #include <net/flow_dissector.h>
 
 struct flow_match {