RDMA/mlx5: Don't rely on FW to set zeros in ECE response

The FW returns zeros in case feature is not enabled, but it is better to
have the capability check and ensure that returned result is cleared.

Fixes: 3e09a427 ("RDMA/mlx5: Get ECE options from FW during create QP")
Link: https://lore.kernel.org/r/20200602125548.172654-3-leon@kernel.orgSigned-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/mlx5/qp.c

@@ -1906,7 +1906,8 @@ static int create_xrc_tgt_qp(struct mlx5_ib_dev *dev, struct mlx5_ib_qp *qp,
 
 	base->container_mibqp = qp;
 	base->mqp.event = mlx5_ib_qp_event;
-	params->resp.ece_options = MLX5_GET(create_qp_out, out, ece);
+	if (MLX5_CAP_GEN(mdev, ece_support))
+		params->resp.ece_options = MLX5_GET(create_qp_out, out, ece);
 
 	spin_lock_irqsave(&dev->reset_flow_resource_lock, flags);
 	list_add_tail(&qp->qps_list, &dev->qp_list);
@@ -2082,7 +2083,8 @@ static int create_user_qp(struct mlx5_ib_dev *dev, struct ib_pd *pd,
 
 	base->container_mibqp = qp;
 	base->mqp.event = mlx5_ib_qp_event;
-	params->resp.ece_options = MLX5_GET(create_qp_out, out, ece);
+	if (MLX5_CAP_GEN(mdev, ece_support))
+		params->resp.ece_options = MLX5_GET(create_qp_out, out, ece);
 
 	get_cqs(qp->type, init_attr->send_cq, init_attr->recv_cq,
 		&send_cq, &recv_cq);