IB/core: Fix and clean up ib_ud_header_init()

ib_ud_header_init() first clears header and then fills up the various
fields.  Later on, it tests header->immediate_present, which it has
already cleared, so the condition is always false.  Fix this by adding
an immediate_present parameter and setting header->immediate_present
as is done with grh_present.  Also remove unused calculation of
header_len.

Signed-off-by: Eli Cohen <eli@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
diff --git a/drivers/infiniband/hw/mthca/mthca_qp.c b/drivers/infiniband/hw/mthca/mthca_qp.c
index c10576f..d2d172e 100644
--- a/drivers/infiniband/hw/mthca/mthca_qp.c
+++ b/drivers/infiniband/hw/mthca/mthca_qp.c
@@ -1494,7 +1494,7 @@
 	u16 pkey;
 
 	ib_ud_header_init(256, /* assume a MAD */
-			  mthca_ah_grh_present(to_mah(wr->wr.ud.ah)),
+			  mthca_ah_grh_present(to_mah(wr->wr.ud.ah)), 0,
 			  &sqp->ud_header);
 
 	err = mthca_read_ah(dev, to_mah(wr->wr.ud.ah), &sqp->ud_header);