i40e: Properly check allowed advertisement capabilities

The i40e_set_link_ksettings and i40e_get_link_ksettings use different
codepaths to check available and supported advertisement modes. This
creates scenarios where it's possible to set a mode that's not allowed,
resulting in a link down.

Fix setting advertisement in i40e_set_link_ksettings by calling
i40e_get_link_ksettings to check what modes are allowed.

Signed-off-by: Jan Sokolowski <jan.sokolowski@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>