octeontx2-pf: Fix TSOv6 offload

HW adds segment size to the payload length
in the IPv6 header. Fix payload length to
just TCP header length instead of 'TCP header
size + IPv6 header size'.

Fixes: 86d74760 ("octeontx2-pf: TCP segmentation offload support")
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: Ratheesh Kannoth <rkannoth@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c

@@ -652,9 +652,7 @@ static void otx2_sqe_add_ext(struct otx2_nic *pfvf, struct otx2_snd_queue *sq,
 				htons(ext->lso_sb - skb_network_offset(skb));
 		} else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6) {
 			ext->lso_format = pfvf->hw.lso_tsov6_idx;
-
-			ipv6_hdr(skb)->payload_len =
-				htons(ext->lso_sb - skb_network_offset(skb));
+			ipv6_hdr(skb)->payload_len = htons(tcp_hdrlen(skb));
 		} else if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4) {
 			__be16 l3_proto = vlan_get_protocol(skb);
 			struct udphdr *udph = udp_hdr(skb);