net/mlx5e: Split open/close channels to stages

As a foundation for safe config flow, a simple clear API such as
(Open then Activate) where the "Open" handles the heavy unsafe
creation operation and the "activate" will be fast and fail safe,
to enable the newly created channels.

For this we split the RQs/TXQ SQs and channels open/close flows to
open => activate, deactivate => close.

This will simplify the ability to have fail safe configuration changes
in downstream patches as follows:

make_new_config(new_params)
{
     old_channels = current_active_channels;
     new_channels = create_channels(new_params);
     if (!new_channels)
              return "Failed, but current channels still active :)"
     deactivate_channels(old_channels); /* Can't fail */
     activate_channels(new_channels); /* Can't fail */
     close_channels(old_channels);
     current_active_channels = new_channels;

     return "SUCCESS";
}

Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>