Region signaling

Region signaling is an optional feature in AXI4.
When you use region identifiers, it means that a single physical interface on a subordinate can
provide multiple logical interfaces. Each logical interface can have a different location in the system
address map.
When the region identifier is used, the subordinate does not have to support the address decode
between the different logical interfaces.
Region signaling uses two 4-bit region identifiers, AWREGION and ARREGION. These region
identifiers can uniquely identify up to 16 different regions.