iavf: replace i40e variables with iavf

Update the old variables and flags marked as i40e to match
the iavf name of the driver.

Signed-off-by: Alice Michael <alice.michael@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>