net/mlx5: add OS specific flow create and destroy

net/mlx5: add OS specific flow create and destroy

This patch introduces the OS specific functions, for flow create
and flow destroy operations.

In existing implementation, the functions to create objects
(flow/table/matcher) return a pointer to the created object.
The functions to destroy objects return 0 on success and errno on
failure.

The new OS specific functions to create objects return 0 on success,
and (-1) on failure.
On success, a pointer to the created object is returned using an
additional parameter.

Signed-off-by: Dekel Peled <dekelp@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>