net/mlx5e: Check ets capability before ets query FW command

On dcbnl callback getpgtccfgtx, the driver should check the ets
capability before ets query command is sent to firmware.
It is valid to return from this void function without changing in/out
parameters, as these parameters are initialized to
DCB_ATTR_VALUE_UNDEFINED.

Fixes: 3a6a931dfb8e ("net/mlx5e: Support DCBX CEE API")
Signed-off-by: Moshe Shemesh <moshe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

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

@@ -511,6 +511,11 @@ static void mlx5e_dcbnl_getpgtccfgtx(struct net_device *netdev,
 	struct mlx5e_priv *priv = netdev_priv(netdev);
 	struct mlx5_core_dev *mdev = priv->mdev;
 
+	if (!MLX5_CAP_GEN(priv->mdev, ets)) {
+		netdev_err(netdev, "%s, ets is not supported\n", __func__);
+		return;
+	}
+
 	if (priority >= CEE_DCBX_MAX_PRIO) {
 		netdev_err(netdev,
 			   "%s, priority is out of range\n", __func__);