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)

- replace brief with name where required
- remove some unwanted empty lines
- fix missing closing doxygen name block