gso: remove vxlan header include file dependency

vxlan will be moved to a plugin. Remove vnet files from including
vxlan header include files.

Type: fix

Signed-off-by: Steven Luong <sluong@cisco.com>
Change-Id: I4268110b4ed54f7ae3ffecd6db0e3025122fa59c
diff --git a/src/vnet/gso/hdr_offset_parser.h b/src/vnet/gso/hdr_offset_parser.h
index 999a278..08037f5 100644
--- a/src/vnet/gso/hdr_offset_parser.h
+++ b/src/vnet/gso/hdr_offset_parser.h
@@ -23,7 +23,8 @@
 #include <vnet/udp/udp_packet.h>
 #include <vnet/tcp/tcp_packet.h>
 #include <vnet/vnet.h>
-#include <vnet/vxlan/vxlan_packet.h>
+
+#define VXLAN_HEADER_SIZE 8
 
 #define foreach_gho_flag        \
   _( 0, IP4)                    \
@@ -437,7 +438,7 @@
       if (UDP_DST_PORT_vxlan == clib_net_to_host_u16 (udp->dst_port))
 	{
 	  gho->gho_flags |= GHO_F_VXLAN_TUNNEL;
-	  gho->hdr_sz += sizeof (vxlan_header_t);
+	  gho->hdr_sz += VXLAN_HEADER_SIZE;
 	}
       else if (UDP_DST_PORT_geneve == clib_net_to_host_u16 (udp->dst_port))
 	{