Many simple kconfig configurations are added to boards and brought in with the board name.
This makes a common import of these configs so one only requires adding a BOARD.config without having to alter the makefile.
This introduces KCONFIG_BOARD_CONFIG and KCONFIG_CPU_CONFIG variable for
boards and CPUs (including common directories) to add default
configuration files to be merged. The current approach, as it uses
Makefile.features, would include boards first, not allowing them to
override CPU configurations.
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.
The softdevice is only verified to be working on nrf52832-based
boards. This feature prevents the softdevice from being build for
other, similar targets (e.g. nrf52840-based boards).
The file always exist so no need to do '-include'.
Replaced using:
sed -i 's|-\(include $(RIOTCPU)/.*/Makefile.features\)|\1|' \
$(git grep -l '$(RIOTCPU)/.*/Makefile.features' boards)
