bnxt_en: Report FEC settings to ethtool.

Implement .get_fecparam() method to report the configured and active FEC
settings.  Also report the supported and advertised FEC settings to
the .get_link_ksettings() method.

Reviewed-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>