net: remove unnecessary includes from net/flow.h

This file is included by a lot of other commonly included
headers, it doesn't need socket.h or flow_dissector.h.

This reduces the size of this file after pre-processing
from 28165 to 4663.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/flow.h

@@ -8,12 +8,13 @@
 #ifndef _NET_FLOW_H
 #define _NET_FLOW_H
 
-#include <linux/socket.h>
 #include <linux/in6.h>
 #include <linux/atomic.h>
-#include <net/flow_dissector.h>
+#include <linux/container_of.h>
 #include <linux/uidgid.h>
 
+struct flow_keys;
+
 /*
  * ifindex generation is per-net namespace, and loopback is
  * always the 1st device in ns (see net_dev_init), thus any