macsec: Enable devices to advertise whether they update sk_buff md_dst during offloads

commit 475747a1 upstream.

Omit rx_use_md_dst comment in upstream commit since macsec_ops is not
documented.

Cannot know whether a Rx skb missing md_dst is intended for MACsec or not
without knowing whether the device is able to update this field during an
offload. Assume that an offload to a MACsec device cannot support updating
md_dst by default. Capable devices can advertise that they do indicate that
an skb is related to a MACsec offloaded packet using the md_dst.

Cc: Sabrina Dubroca <sd@queasysnail.net>
Cc: stable@vger.kernel.org
Fixes: 860ead89

 ("net/macsec: Add MACsec skb_metadata_dst Rx Data path support")
Signed-off-by: Rahul Rameshbabu <rrameshbabu@nvidia.com>
Reviewed-by: Benjamin Poirier <bpoirier@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://lore.kernel.org/r/20240423181319.115860-2-rrameshbabu@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>