i40e: Allow user to change link settings if link is down

Allow the user to change auto-negotiation and speed settings if
link is down.

Change-ID: I372967c627682b5e1835f623a7cbf41b21b51043
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>