net/mlx5: Add hash table for flow groups in flow table

When adding a flow table entry (fte) to a flow table (ft), we first
need to find its flow group (fg). Currently, this is done by
traversing a linear list of all flow groups in the flow table.
Furthermore, since multiple flow groups which correspond to the same
fte mask may exist in the same ft, we can't just stop at the first
match. Converting the linear list to rhltable in order to speed things
up.

The last four patches increases the steering rules update rate by a
factor of more than 7 (for insertion of 50K steering rules).

Signed-off-by: Matan Barak <matanb@mellanox.com>
Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>