net/mlx5: DR, Add Steering entry (STE) utilities

Steering Entry (STE) object is the basic building block of the steering
map. There are several types of STEs. Each rule can be constructed of
multiple STEs. Each STE dictates which fields of the packet's header are
being matched as well as the information about the next step in map (hit
and miss pointers). The hardware gets a packet and tries to match it
against the STEs, going to either the hit pointer or the miss pointer.
This file handles the STE operations.

Signed-off-by: Alex Vesker <valex@mellanox.com>
Signed-off-by: Erez Shitrit <erezsh@mellanox.com>
Reviewed-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>