i40e: Wrong 'Advertised FEC modes' after set FEC to AUTO

Fix display of parameters "Configured FEC encodings:" and "Advertised
FEC modes:" in ethtool.  Implemented by setting proper FEC bits in
“advertising” bitmask of link_modes struct and “fec” bitmask in
ethtool_fecparam struct. Without this patch wrong FEC settings
can be shown.

Signed-off-by: Jaroslaw Gawin <jaroslawx.gawin@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>