Implement set_settings for ethtool in i40e.

Change-ID: Ie3c3fe18e8ff86c3f25b842844b3d9aabc9bba57
Signed-off-by: Catherine Sullivan <catherine.sullivan@intel.com>
Tested-by: Jim Young <jamesx.m.young@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>