net/mlx5e: Check for qos capability in dcbnl_initialize

[ Upstream commit 33c52b67 ]

qos capability is the master capability bit that determines
if the DCBX is supported for the PCI function. If this bit is off,
driver cannot run any dcbx code.

Fixes: e207b7e9 ("net/mlx5e: ConnectX-4 firmware support for DCBX")
Signed-off-by: Huy Nguyen <huyn@mellanox.com>
Reviewed-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/ethernet/mellanox/mlx5/core/en_dcbnl.c

@@ -754,6 +754,9 @@ void mlx5e_dcbnl_initialize(struct mlx5e_priv *priv)
 {
 	struct mlx5e_dcbx *dcbx = &priv->dcbx;
 
+	if (!MLX5_CAP_GEN(priv->mdev, qos))
+		return;
+
 	if (MLX5_CAP_GEN(priv->mdev, dcbx))
 		mlx5e_dcbnl_query_dcbx_mode(priv, &dcbx->mode);