eth: igc: migrate to new RXFH callbacks

eth: igc: migrate to new RXFH callbacks

Migrate to new callbacks added by commit 9bb00786fc61 ("net: ethtool:
add dedicated callbacks for getting and setting rxfh fields").

Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Reviewed-by: Joe Damato <joe@dama.to>
Reviewed-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250614180907.4167714-3-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>