cpu/stm32: adapt gpio driver to default CMSIS exti structure
cpu/stm32: adapt gpio driver to default CMSIS exti structure

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