iavf: move i40evf files to new name

Simply move the i40evf files to the new name, updating the #includes
to track the new names, and updating the Makefile as well.

A future patch will remove the i40e references (after the code
removal patches later in this series).

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>