i40e: fix the restart auto-negotiation after FEC modified

When FEC mode was changed the link didn't know it because
the link was not reset and new parameters were not negotiated.
Set a flag 'I40E_AQ_PHY_ENABLE_ATOMIC_LINK' in 'abilities'
to restart the link and make it run with the new settings.

Fixes: 1d963401

 ("i40e: Add support FEC configuration for Fortville 25G")
Signed-off-by: Jaroslaw Gawin <jaroslawx.gawin@intel.com>
Signed-off-by: Mateusz Palczewski <mateusz.palczewski@intel.com>
Tested-by: Dave Switzer <david.switzer@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>