net/mlx5: Use flow steering infrastructure for mlx5_en

Expose the new flow steering API and remove the old
one.

Few changes are required:

1. The Ethernet flow steering follows the existing implementation, but uses
the new steering API. The old flow steering implementation is removed.

2. Move the E-switch FDB management to use the new API.

3. When driver is loaded call to mlx5_init_fs which initialize
the flow steering tree structure, open namespaces for NIC receive
and for E-switch FDB.

4. Call to mlx5_cleanup_fs when the driver is unloaded.

Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>