tg3: Use skb_is_gso_v6()

This patch converts the driver to prefer the skb_is_gso_v6() helper over
the explicit inlined version.
Reviewed-by: Benjamin Li <benli@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/tg3.c

@@ -5574,9 +5574,9 @@ static netdev_tx_t tg3_start_xmit(struct sk_buff *skb,
 			goto out_unlock;
 		}
 
-		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
+		if (skb_is_gso_v6(skb)) {
 			hdrlen = skb_headlen(skb) - ETH_HLEN;
-		else {
+		} else {
 			struct iphdr *iph = ip_hdr(skb);
 
 			tcp_opt_len = tcp_optlen(skb);
@@ -5798,7 +5798,7 @@ static netdev_tx_t tg3_start_xmit_dma_bug(struct sk_buff *skb,
 		iph = ip_hdr(skb);
 		tcp_opt_len = tcp_optlen(skb);
 
-		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6) {
+		if (skb_is_gso_v6(skb)) {
 			hdr_len = skb_headlen(skb) - ETH_HLEN;
 		} else {
 			u32 ip_tcp_len;