Lopcomm part of the SR already has some partial support for cell_list: if multiple cells are defined there enb.cfg will have multiple CPRI radio units and multiple cells configured. But so far all promises, except cpri-link, were done only for one RU.

-> Fix that by starting to generalize RUlib code to handle multiple radio units, invoking model-specific RU driver for each RU, and adjusting ru/lopcomm instance code to correctly generate and activate different promises for different radio units.

After the patch multiRU support is still very incomplete, but it is a step forward.

/cc @jhuge, @lu.xu, @xavier_thompson, @Daetalus