Added get_rxfh_indir_size, get_rxfh_key_size and get_rxfh ethtool_ops
callbacks implementations.

This enables the ethtool's "-x" and "--show-rxfh[-indir]" options.
Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>