ex of use:
./simple.py litex_boards.platform.ulx3s --build --load
./simple.py litex_boards.platform.trellisboard --build --load
./simple.py litex_boards.platform.arty --build --load
etc...

targets/EthernetSoC: be sure memory region is added before adding Wishbone Slave (required by new SoC)

We initially wanted to provide different level of support for the platforms/targets, mainly
to avoid too much maintenance and let each contributor update its contributed platforms and
targets, but it's easier to update all platforms/targets all-together when LiteX evolves or
changes (and that's what has been done on litex-boards since the creation of the repository).
So let just simplify things and avoid this differentiation.