net/mlx5: remove flow support

net/mlx5: remove flow support

This start a series to re-work the flow engine in mlx5 to easily support
flow conversion to Verbs or TC.  This is necessary to handle both regular
flows and representors flows.

As the full file needs to be clean-up to re-write all items/actions
processing, this patch starts to disable the regular code and only let the
PMD to start in isolated mode.

After this patch flow API will not be usable.

Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
Acked-by: Yongseok Koh <yskoh@mellanox.com>