net/mlx5_core: Add flow steering lookup algorithms

Introduce the flow steering mlx5_flow_namespace (Namespace)
and fs_prio (Flow Steering Priority) tree nodes.

Namespaces are used in order to isolate different usages or types
of steering (for example, downstream patches will add a different
namespaces for the NIC driver and for E-Switch FDB usages).

Flow Steering Priorities are objects that describes priorities
ranges between different flow objects under the same namespace.

Example, entries in priority i are matched before entries
in priority i+1.

This patch adds the following algorithms:

1) Calculate level:
Each flow table has level(the priority between the flow tables).
When we initialize the flow steering tree, we assign range of levels
to each priority, therefore the level for new flow table is
the location within the priority related to the range of the priority.

2) Match between match criteria. This function is used
for searching flow group when new flow rule is added.

3) Match between match values. This function is used
for searching flow table entry  when new flow rule is added.

4) Add essential macros for traversing on a node's children.
E.g. traversing on all the flow table of some priority

Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>