openvswitch: Restructure datapath.c and flow.c

Over the time datapath.c and flow.c has became pretty large files.
Following patch restructures functionality of component into three
different components:

flow.c: contains flow extract.
flow_netlink.c: netlink flow api.
flow_table.c: flow table api.

This patch restructures code without changing logic.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: Jesse Gross <jesse@nicira.com>
diff --git a/net/openvswitch/datapath.h b/net/openvswitch/datapath.h
index 2c15541..a6982ef 100644
--- a/net/openvswitch/datapath.h
+++ b/net/openvswitch/datapath.h
@@ -27,6 +27,7 @@
 #include <linux/u64_stats_sync.h>
 
 #include "flow.h"
+#include "flow_table.h"
 #include "vport.h"
 
 #define DP_MAX_PORTS           USHRT_MAX