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.
The RTT overflow callback is not available on all RTT implementations.
This means it is either a no-op or `rtt_set_overflow_cb()` is a no-op
or it will overwrite the alarm set with `rtt_set_alarm()`.
This adds a feature to indicate that proper overflow reporting is available.
Some periph_rtt implementations do not provide `rtt_set_counter()`. This
adds `periph_rtt_set_counter` as feature to allow testing for its
availability. The feature is provided at CPU level if periph_rtt is
provided by the board for all CPUs implementing `rtt_set_counter()`.
MCG_Lite is used in many KL parts and is a less advanced clock generator
than the full MCG used in the K series. This change lets the MCG_Lite
and MCG share the same user facing API, with some configuration
differences.
Now that CPU and CPU_MODEL are defined in the board's Makefile.features
it can be used to determine the available features provided by the
specific model.
This removes doing `filter-out periph_hwrng, $(FEATURES_PROVIDED)`
after processing `cpu/$(CPU)/Makefile.features`.
The current solution is a HACK as `CPU_MODEL` is currently not available
at that moment but will be in the near future.
It will allow always including `cpu/$(CPU)/Makefile.features` after
`boards/$(BOARD)/Makefile.features`.
It is a part of moving `CPU/CPU_MODEL` definitions to `Makefile.features`.
