Cleanup warnings with W=1 and enforce on CI

We have a lot of functions that should be static or could be removed since they are unused. We should clean that up.

added Improvement label

assigned to @demarchi

mentioned in merge request ci!8 (merged)

All the warnings are now fixed, except for display. Display needs a lot of ifdefs to avoid static functions showing as "defined but not used". I changed the CI part to build the driver without display when checking W=1

closed