This gets rid of a long list of boards with network interfaces and
instead let's boards (or MCUs with peripheral network interfaces)
provide the netif feature.
The apps that before used the long list are not depending on the
feature instead (in case of the default example, this is an
optional dependency).
Co-authored-by: mguetschow <mikolai.guetschow@tu-dresden.de>
Co-authored-by: mewen.berthelot <mewen.berthelot@orange.com>
cpu/$(CPU)/Makefile.features and cpu/$(CPU)/Makefile.dep are
automatically included
Part of moving CPU/CPU_MODEL definition to Makefile.features to have it
available before Makefile.include.
