bna: use new helper tcp_v6_gso_csum_prep

Use new helper tcp_v6_gso_csum_prep in additional network drivers.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/brocade/bna/bnad.c

@@ -2504,12 +2504,7 @@ bnad_tso_prepare(struct bnad *bnad, struct sk_buff *skb)
 					   IPPROTO_TCP, 0);
 		BNAD_UPDATE_CTR(bnad, tso4);
 	} else {
-		struct ipv6hdr *ipv6h = ipv6_hdr(skb);
-
-		ipv6h->payload_len = 0;
-		tcp_hdr(skb)->check =
-			~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr, 0,
-					 IPPROTO_TCP, 0);
+		tcp_v6_gso_csum_prep(skb);
 		BNAD_UPDATE_CTR(bnad, tso6);
 	}