i40e: loopback info and set loopback fix

Add information about current loopback mode to data returned from
get_link_info function. Minor fix in set_loopback function and
update in loopback types enum.

Change-Id: I9d1c540a84ab18eef5ea6429be6331f33fc06aca
Signed-off-by: Kamil Krawczyk <kamil.krawczyk@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>