cpu/stm32: remove useless ifdef around DMA definitions
cpu/stm32: remove useless ifdef around DMA definitions

kaspar030/RIOT,OTAkeys/RIOT,basilfx/RIOT,authmillenon/RIOT,OTAkeys/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,miri64/RIOT,OlegHahm/RIOT,basilfx/RIOT,jasonatran/RIOT,ant9000/RIOT,kYc0o/RIOT,jasonatran/RIOT,miri64/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,miri64/RIOT,jasonatran/RIOT,ant9000/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,OlegHahm/RIOT,miri64/RIOT,basilfx/RIOT,kYc0o/RIOT,kaspar030/RIOT,ant9000/RIOT,ant9000/RIOT,authmillenon/RIOT,jasonatran/RIOT,OTAkeys/RIOT,miri64/RIOT,kYc0o/RIOT,basilfx/RIOT,kaspar030/RIOT,ant9000/RIOT,OTAkeys/RIOT,authmillenon/RIOT,kaspar030/RIOT,kYc0o/RIOT,authmillenon/RIOT,basilfx/RIOT,OTAkeys/RIOT,OlegHahm/RIOT