[TCP]: Introduce tcp_hdrlen() and tcp_optlen()

The ip_hdrlen() buddy, created to reduce the number of skb->h.th-> uses and to
avoid the longer, open coded equivalent.

Ditched a no-op in bnx2 in the process.

I wonder if we should have a BUG_ON(skb->h.th->doff < 5) in tcp_optlen()...

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/netxen/netxen_nic_main.c b/drivers/net/netxen/netxen_nic_main.c
index b548a30..b488e94 100644
--- a/drivers/net/netxen/netxen_nic_main.c
+++ b/drivers/net/netxen/netxen_nic_main.c
@@ -779,7 +779,7 @@
 		if (skb_shinfo(skb)->gso_size > 0) {
 
 			no_of_desc++;
-			if ((ip_hdrlen(skb) + skb->h.th->doff * 4 +
+			if ((ip_hdrlen(skb) + tcp_hdrlen(skb) +
 			     sizeof(struct ethhdr)) >
 			    (sizeof(struct cmd_desc_type0) - 2)) {
 				no_of_desc++;