Remove confusing distclean/clean dichotomy
Remove confusing distclean/clean dichotomy

in the top level, make clean cleans all stlink code.
in an application level, it only cleans that application

ros2/stlink,braincorp/stlink,12019/stlink,trigrass2/stlink,gtalusan/stlink,ros2/stlink,chaosAD/stlink,karlp/kkstm32_base,trigrass2/stlink,simonjwright/stlink,braincorp/stlink,gtalusan/stlink,swegener/stlink,fedorcomander/stlink,fedorcomander/stlink,chaosAD/stlink,simonjwright/stlink,12019/stlink,swegener/stlink