Add description of a the unit a module is connected to

[imphil]

Currently we can read the available debug modules from the OSD system, but we can only guess which unit in the observed system the module is connected to. For example, we might know there's a CTM at address 4, but we don't know (without knowing the hardware) if this module is connected to cpu0 or cpu1. Adding an identifier which describes the module in the observed system as a register to CTM, STM, MAM and other debug modules would help discoverability from the software side.