cpu/stm32: remove redundant variables computations
cpu/stm32: remove redundant variables computations

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