The periph_dma is not pulled in automatically for all applications.
Applications willing to use the configured peripherals with periph_dma
for a given board will have to include the feature explictly in their
Makefile.
It was causing unrelated issues as threads got de-scheduled while
calling printf and this was not handled properly in tests at that
moment.
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)
