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)
Since wsn430-v1_3b and wsn430-v1_4 do have different radio
configurations we need to separate `board.h` for them, so this moves
their currently common `board.h` to `board_common.h` to be included by
later introduced `board.h`