net/mlx5: Add support for flow table destination number

Add support to set a destination from a flow table number.
This functionality will be used in downstream patches from this
series by the DEVX stuff.

Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Acked-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>