IB/mlx5: Add PCI write end padding support

Add the PCI write end padding flag to device_cap_flags enum and set it
during mlx5_ib_query_device so it will be reported to user-space.

During WQ/QP creation, set that capability for WQ/QP if user requested
it and HW supports it.

PCI write end padding modification is not supported for now. There's no
such flag for a QP but for a WQ, create and modify use the same flag.
Return an error if PCI write end padding flag is set during modify_wq.

Signed-off-by: Noa Osherovich <noaos@mellanox.com>
Reviewed-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h
index 0a328d6..6dd8cac 100644
--- a/drivers/infiniband/hw/mlx5/mlx5_ib.h
+++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h
@@ -228,6 +228,7 @@ struct wr_list {
 
 enum mlx5_ib_rq_flags {
 	MLX5_IB_RQ_CVLAN_STRIPPING	= 1 << 0,
+	MLX5_IB_RQ_PCI_WRITE_END_PADDING	= 1 << 1,
 };
 
 struct mlx5_ib_wq {
@@ -421,7 +422,7 @@ enum mlx5_ib_qp_flags {
 	MLX5_IB_QP_RSS				= 1 << 8,
 	MLX5_IB_QP_CVLAN_STRIPPING		= 1 << 9,
 	MLX5_IB_QP_UNDERLAY			= 1 << 10,
-	/* Reserved for PCI_WRITE_PAD 		= 1 << 11, */
+	MLX5_IB_QP_PCI_WRITE_END_PADDING	= 1 << 11,
 	MLX5_IB_QP_TUNNEL_OFFLOAD		= 1 << 12,
 };