Adding a new platform: renesas rz

[Michele Bisogno]

> Renesas offers different architectures in their portfolio[1], I haven't
> dug into the OpenWRT build system for this issue yet to tell whether it
> is able to handle that at this folder level. Much of the above is
> "legacy" and does not run OpenWRT(?), but they also seem to aim for
> Risc-V. There is a platform called "ramips" and the broadcoms each have
> their own subdirectory. None of them have punctuation yet. Maybe call it
> "renesasrz"? They're also offering other ARM-based SoCs, and building
> common kernels might become difficult.
> Torsten
> [1] https://www.renesas.com/eu/en/products/microcontrollers-microprocessors/other-mcus-mpus

Hi Torsten,

what is listed there is old stuff. Renesas MPUs are now all under the
RZ umbrella.
Well, actually there are also the rcar devices, but these are automotive SoCs.
Yes, there is an RZ device that is not Arm: RZ/Five. For now it is a
single device based on a Andes core.

Kind regards,
Michele