net/mlx5: Fix HW spec violation configuring uplink

Make sure to modify uplink port to follow only if the uplink_follow
capability is set as required by the HW spec. Failure to do so causes
traffic to the uplink representor net device to cease after switching to
switchdev mode.

Fixes: 7d0314b ("net/mlx5e: Modify uplink state on interface up/down")
Signed-off-by: Eli Cohen <elic@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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

@@ -1107,8 +1107,9 @@ static void mlx5e_uplink_rep_enable(struct mlx5e_priv *priv)
 
 	mlx5e_rep_tc_enable(priv);
 
-	mlx5_modify_vport_admin_state(mdev, MLX5_VPORT_STATE_OP_MOD_UPLINK,
-				      0, 0, MLX5_VPORT_ADMIN_STATE_AUTO);
+	if (MLX5_CAP_GEN(mdev, uplink_follow))
+		mlx5_modify_vport_admin_state(mdev, MLX5_VPORT_STATE_OP_MOD_UPLINK,
+					      0, 0, MLX5_VPORT_ADMIN_STATE_AUTO);
 	mlx5_lag_add(mdev, netdev);
 	priv->events_nb.notifier_call = uplink_rep_async_event;
 	mlx5_notifier_register(mdev, &priv->events_nb);