IB/mlx4: Take sizeof the correct pointer in call to memset()

When clearing the ib_ah_attr parameter in to_ib_ah_attr(), use sizeof
*ib_ah_attr instead of sizeof *path.  This is the same bug as was
fixed for mthca in 99d4f22e ("IB/mthca: Use correct structure size in
call to memset()"), but the code was cut and pasted into mlx4 before the
fix was merged.
Signed-off-by: Dotan Barak <dotanb@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/mlx4/qp.c

@@ -1498,7 +1498,7 @@ static int to_ib_qp_access_flags(int mlx4_flags)
 static void to_ib_ah_attr(struct mlx4_dev *dev, struct ib_ah_attr *ib_ah_attr,
 				struct mlx4_qp_path *path)
 {
-	memset(ib_ah_attr, 0, sizeof *path);
+	memset(ib_ah_attr, 0, sizeof *ib_ah_attr);
 	ib_ah_attr->port_num	  = path->sched_queue & 0x40 ? 2 : 1;
 
 	if (ib_ah_attr->port_num == 0 || ib_ah_attr->port_num > dev->caps.num_ports)