igc: Change byte order in struct igc_nfc_filter

Every time we access the 'etype' and 'vlan_tci' fields from struct
igc_nfc_filter to enable or disable filters in hardware we have to
convert them from big endian to host order so it makes more sense to
simply have these fields in host order.

The byte order conversion should take place in igc_ethtool_get_nfc_
rule() and igc_ethtool_add_nfc_rule(), which are called by .get_rxnfc
and .set_rxnfc ethtool ops, since ethtool subsystem is the one who deals
with them in big endian order.

Signed-off-by: Andre Guedes <andre.guedes@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>