net/mlx5: Add direct rule fs_cmd implementation

Add support to create flow steering objects
via direct rule API (SW steering).
New layer is added - fs_dr, this layer translates the command that
fs_core sends to the FW into direct rule API. In case that direct
rule is not supported in some feature then -EOPNOTSUPP is
returned.

Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Reviewed-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>