openvswitch: Use regular GRE net_device instead of vport

Using GRE tunnel meta data collection feature, we can implement
OVS GRE vport. This patch removes all of the OVS
specific GRE code and make OVS use a ip_gre net_device.
Minimal GRE vport is kept to handle compatibility with
current userspace application.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/gre.h b/include/net/gre.h
index b531820..e3e0845 100644
--- a/include/net/gre.h
+++ b/include/net/gre.h
@@ -33,16 +33,8 @@
 int gre_cisco_register(struct gre_cisco_protocol *proto);
 int gre_cisco_unregister(struct gre_cisco_protocol *proto);
 
-void gre_build_header(struct sk_buff *skb, const struct tnl_ptk_info *tpi,
-		      int hdr_len);
-
-static inline struct sk_buff *gre_handle_offloads(struct sk_buff *skb,
-						  bool csum)
-{
-	return iptunnel_handle_offloads(skb, csum,
-					csum ? SKB_GSO_GRE_CSUM : SKB_GSO_GRE);
-}
-
+struct net_device *gretap_fb_dev_create(struct net *net, const char *name,
+				       u8 name_assign_type);
 
 static inline int ip_gre_calc_hlen(__be16 o_flags)
 {