i40e: always set ks->base.speed in i40e_get_settings_link_up

In i40e_get_settings_link_up, set ks->base.speed to SPEED_UNKNOWN
in the case where we don't know the link speed.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>