i40e: don't restart nway if autoneg not supported

On link types that do not support autoneg, we cannot attempt to restart
nway negotiation. This results in a dead link that requires a power
cycle to remedy.

Fix this by saving off the autoneg state and checking this value before
we try to restart nway.

Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>