net/cxgb3: fix revert error

728e2cc Revert "cxgb3: Check and handle the dma mapping errors"

reverted f83331b cxgb3: Check and handle the dma mapping errors, however, in between those two there was also
be8b678 cxgb3: Correct comparisons and calculations using skb->tail and skb-transport_header and
15dd16c cxgb3: Correct comparisons and calculations using skb->tail and skb-transport_header

The author of the revert did not fix up the conflicts in such as way as to preserve the other two commits, so they were reverted too. As they correct math issues under certain conditions, they should be retained. This puts them back in place.

---
 drivers/net/ethernet/chelsio/cxgb3/sge.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

b/drivers/net/ethernet/chelsio/cxgb3/sge.c
index 9c89dc8..632b318 100644

@@ -1599,7 +1599,8 @@ static void write_ofld_wr(struct adapter *adap,

struct sk_buff *skb,
flits = skb_transport_offset(skb) / 8;
sgp = ndesc == 1 ? (struct sg_ent *)&d->flit[flits] : sgl; sgl_flits = make_sgl(skb, sgp, skb_transport_header(skb),

-			     skb->tail - skb->transport_header,
+			     skb_tail_pointer(skb) -
+			     skb_transport_header(skb),

adap->pdev);
if (need_skb_unmap()) {
setup_deferred_unmapping(skb, adap->pdev, sgp, sgl_flits);

1.8.1.4