eth: sxgbe: migrate to new RXFH callbacks

Migrate to new callbacks added by commit 9bb00786 ("net: ethtool:
add dedicated callbacks for getting and setting rxfh fields").

RXFH is all this driver supports in RXNFC so old callbacks are
completely removed.

Reviewed-by: Joe Damato <joe@dama.to>
Link: https://patch.msgid.link/20250617014848.436741-6-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>