i40e/i40evf: i40e implementation for skb_set_hash

Original comment from Tom Herbert <therbert@google.com>

   Drivers should call skb_set_hash to set the hash and its type
   in an skbuff.

This patch builds upon Tom's original implementation and adds
the L4 type return when we know it is an L4 hash.
This requires use of the ptype decoder ring, so enable it.

Change-ID: I2f9fa86d1a6add58cff13386f7f4238b1abcc468
CC: Tom Herbert <therbert@google.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Acked-by: Shannon Nelson <shannon.nelson@intel.com>
Acked-by: Mitch Williams <mitch.a.williams@intel.com>
Signed-off-by: Catherine Sullivan <catherine.sullivan@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>