net/mlx5: Added missing definitions in preparation for HW Steering

As part of preparation for HWS, added missing definitions
in qp.h and fs_core.h:

 - FS_FT_FDB_RX/TX table types that are used by HWS in addition
   to an existing FS_FT_FDB
 - MLX5_WQE_CTRL_INITIATOR_SMALL_FENCE that is used by HWS to
   require fence in WQE

Reviewed-by: Hamdan Agbariya <hamdani@nvidia.com>
Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>