cpu/stm32: adapt ltdc periph disp_dev interface
cpu/stm32: adapt ltdc periph disp_dev interface

jasonatran/RIOT,jasonatran/RIOT,ant9000/RIOT,ant9000/RIOT,miri64/RIOT,miri64/RIOT,miri64/RIOT,ant9000/RIOT,kaspar030/RIOT,miri64/RIOT,OlegHahm/RIOT,kYc0o/RIOT,OlegHahm/RIOT,kaspar030/RIOT,kYc0o/RIOT,ant9000/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,OlegHahm/RIOT,jasonatran/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,jasonatran/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,miri64/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,ant9000/RIOT,jasonatran/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,kaspar030/RIOT,kYc0o/RIOT