sfc: correctly advertise tunneled IPv6 segmentation

Recent sfc NICs are TSO capable for some tunnel protocols. However, it
was not working properly because the feature was not advertised in
hw_enc_features, but in hw_features only.

Setting up a GENEVE tunnel and using iperf3 to send IPv4 and IPv6 traffic
to the tunnel show, with tcpdump, that the IPv4 packets still had ~64k
size but the IPv6 ones had only ~1500 bytes (they had been segmented by
software, not offloaded). With this patch segmentation is offloaded as
expected and the traffic is correctly received at the other end.

Fixes: 24b2c375 ("sfc: advertise encapsulated offloads on EF10")
Reported-by: Tianhao Zhao <tizhao@redhat.com>
Signed-off-by: Íñigo Huguet <ihuguet@redhat.com>
Acked-by: Martin Habets <habetsm.xilinx@gmail.com>
Link: https://lore.kernel.org/r/20230125143513.25841-1-ihuguet@redhat.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/sfc/efx.c

@@ -1003,8 +1003,11 @@ static int efx_pci_probe_post_io(struct efx_nic *efx)
 	/* Determine netdevice features */
 	net_dev->features |= (efx->type->offload_features | NETIF_F_SG |
 			      NETIF_F_TSO | NETIF_F_RXCSUM | NETIF_F_RXALL);
-	if (efx->type->offload_features & (NETIF_F_IPV6_CSUM | NETIF_F_HW_CSUM))
+	if (efx->type->offload_features & (NETIF_F_IPV6_CSUM | NETIF_F_HW_CSUM)) {
 		net_dev->features |= NETIF_F_TSO6;
+		if (efx_has_cap(efx, TX_TSO_V2_ENCAP))
+			net_dev->hw_enc_features |= NETIF_F_TSO6;
+	}
 	/* Check whether device supports TSO */
 	if (!efx->type->tso_versions || !efx->type->tso_versions(efx))
 		net_dev->features &= ~NETIF_F_ALL_TSO;