net/mlx5: move verbs flows and attributes

net/mlx5: move verbs flows and attributes

Moves ibv_attr containing the specification of the flow from Verbs point
of view also with the verbs flow itself near the related verbs objects
making the flow.

This is also a preparation to handle correctly the RSS hash
configuration provided by the user, has multiple Verbs flows will be
necessary for a single generic flow.

Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
Acked-by: Yongseok Koh <yskoh@mellanox.com>