net/mlx5: add devarg for extensive metadata support

net/mlx5: add devarg for extensive metadata support

The PMD parameter dv_xmeta_en is added to control extensive
metadata support. A nonzero value enables extensive flow
metadata support if device is capable and driver supports it.
This can enable extensive support of MARK and META item of
rte_flow. The newly introduced SET_TAG and SET_META actions
do not depend on dv_xmeta_en parameter, because there is
no compatibility issue for new entities. The dv_xmeta_en is
disabled by default.

There are some possible configurations, depending on parameter
value:

- 0, this is default value, defines the legacy mode, the MARK
  and META related actions and items operate only within NIC Tx
  and NIC Rx steering domains, no MARK and META information
  crosses the domain boundaries. The MARK item is 24 bits wide,
  the META item is 32 bits wide.

- 1, this engages extensive metadata mode, the MARK and META
  related actions and items operate within all supported steering
  domains, including FDB, MARK and META information may cross
  the domain boundaries. The ``MARK`` item is 24 bits wide, the
  META item width depends on kernel and firmware configurations
  and might be 0, 16 or 32 bits. Within NIC Tx domain META data
  width is 32 bits for compatibility, the actual width of data
  transferred to the FDB domain depends on kernel configuration
  and may be vary. The actual supported width can be retrieved
  in runtime by series of rte_flow_validate() trials.

- 2, this engages extensive metadata mode, the MARK and META
  related actions and items operate within all supported steering
  domains, including FDB, MARK and META information may cross
  the domain boundaries. The META item is 32 bits wide, the MARK
  item width depends on kernel and firmware configurations and
  might be 0, 16 or 24 bits. The actual supported width can be
  retrieved in runtime by series of rte_flow_validate() trials.

If there is no E-Switch configuration the ``dv_xmeta_en`` parameter is
ignored and the device is configured to operate in legacy mode (0).

Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>