i40e/i40evf: Refactor tunnel interpretation

Refactor the interpretation of a tunnel.  This removes
some code and lets us start using the hardware's parsing.

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>