Revert "net/mlx5e: Update and set Xon/Xoff upon port speed set"

This reverts commit d243417.
It causes errors when trying to configure QoS, as well as
loss of L2 connectivity (on multi-host devices).

Reported-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/20250910170011.70528106@kernel.org
Fixes: d243417 ("net/mlx5e: Update and set Xon/Xoff upon port speed set")
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Tariq Toukan

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

@@ -139,8 +139,6 @@ void mlx5e_update_carrier(struct mlx5e_priv *priv)
 	if (up) {
 		netdev_info(priv->netdev, "Link up\n");
 		netif_carrier_on(priv->netdev);
-		mlx5e_port_manual_buffer_config(priv, 0, priv->netdev->mtu,
-						NULL, NULL, NULL);
 	} else {
 		netdev_info(priv->netdev, "Link down\n");
 		netif_carrier_off(priv->netdev);