net/mlx5e: Fix error path of updating netdev queues

Avoid division by zero in the error flow. In the driver TC number can be
either 1 or 8. When TC count is set to 1, driver zero netdev->num_tc.
Hence, need to convert it back from 0 to 1 in the error flow.

Fixes: fa374877 ("net/mlx5e: Handle errors from netif_set_real_num_{tx,rx}_queues")
Signed-off-by: Aya Levin <ayal@nvidia.com>
Reviewed-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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

@@ -2697,7 +2697,7 @@ static int mlx5e_update_netdev_queues(struct mlx5e_priv *priv)
 	int err;
 
 	old_num_txqs = netdev->real_num_tx_queues;
-	old_ntc = netdev->num_tc;
+	old_ntc = netdev->num_tc ? : 1;
 
 	nch = priv->channels.params.num_channels;
 	ntc = priv->channels.params.num_tc;