Features must be provided by the board if they're actually
available on board. Other features might be provided by the
CPU.
Some grouping is also removed as it is not necessary.
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)
