net: drv: virtio: migrate to new RXFH callbacks

Add support for the new rxfh_fields callbacks, instead of de-muxing
the rxnfc calls. This driver does not support flow filtering so
the set_rxnfc callback is completely removed.

Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://patch.msgid.link/20250611145949.2674086-9-kuba@kernel.org


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