i40e/i40evf: create and use new unified header file

This moves a header for i40evf to include/linux/avf/virtchnl.h.
The directory name AVF is an acronym for the Intel(R) Adaptive
Virtual Function.

This first step creates the new file, which is a rename of
drivers/net/ethernet/intel/i40evf/i40e_virtchnl.h to
include/linux/avf/virtchnl.h, and should show up in git
as a rename when using git log --follow.

To keep things building after the move, the changes to the i40evf
driver are made to point to the new include file location.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/intel/i40evf/i40e_common.c b/drivers/net/ethernet/intel/i40evf/i40e_common.c
index 6729624..1db028a 100644
--- a/drivers/net/ethernet/intel/i40evf/i40e_common.c
+++ b/drivers/net/ethernet/intel/i40evf/i40e_common.c
@@ -27,7 +27,7 @@
 #include "i40e_type.h"
 #include "i40e_adminq.h"
 #include "i40e_prototype.h"
-#include "i40e_virtchnl.h"
+#include <linux/avf/virtchnl.h>
 
 /**
  * i40e_set_mac_type - Sets MAC type