i40e: Stop dropping 802.1ad tags - eth proto 0x88a8

Enable i40e to pass traffic with VLAN tags using the 802.1ad ethernet
protocol ID (0x88a8).

This requires NIC firmware providing version 1.7 of the API. With
older NIC firmware 802.1ad tagged packets will continue to be dropped.

No VLAN offloads nor RSS are supported for 802.1ad VLANs.

Signed-off-by: Scott Peterson <scott.d.peterson@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>