net/mlx5e: Update max_opened_tc also when channels are closed

max_opened_tc is used for stats, so that potentially non-zero stats
won't disappear when num_tc decreases. However, mlx5e_setup_tc_mqprio
fails to update it in the flow where channels are closed.

This commit fixes it. The new value of priv->channels.params.num_tc is
always checked on exit. In case of errors it will just be the old value,
and in case of success it will be the updated value.

Fixes: 05909bab

 ("net/mlx5e: Avoid reset netdev stats on configuration changes")
Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>