cpu/stm32_common/periph: Fix addr filtering
cpu/stm32_common/periph: Fix addr filtering

- Set MACFFR to unicast filtering

- Change byte-order of the MAC

ant9000/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,ant9000/RIOT,basilfx/RIOT,jasonatran/RIOT,kYc0o/RIOT,OlegHahm/RIOT,yogo1212/RIOT,ant9000/RIOT,jasonatran/RIOT,OTAkeys/RIOT,basilfx/RIOT,OTAkeys/RIOT,jasonatran/RIOT,ant9000/RIOT,smlng/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,smlng/RIOT,kaspar030/RIOT,authmillenon/RIOT,OTAkeys/RIOT,miri64/RIOT,authmillenon/RIOT,miri64/RIOT,jasonatran/RIOT,smlng/RIOT,kaspar030/RIOT,miri64/RIOT,miri64/RIOT,OlegHahm/RIOT,yogo1212/RIOT,authmillenon/RIOT,authmillenon/RIOT,OlegHahm/RIOT,smlng/RIOT,kYc0o/RIOT,OlegHahm/RIOT,kYc0o/RIOT,RIOT-OS/RIOT,basilfx/RIOT,yogo1212/RIOT,ant9000/RIOT,RIOT-OS/RIOT,miri64/RIOT,kYc0o/RIOT,OTAkeys/RIOT,authmillenon/RIOT,kaspar030/RIOT,smlng/RIOT,yogo1212/RIOT,OTAkeys/RIOT,jasonatran/RIOT,kaspar030/RIOT,basilfx/RIOT,yogo1212/RIOT,kaspar030/RIOT,yogo1212/RIOT,OlegHahm/RIOT,basilfx/RIOT,RIOT-OS/RIOT