cpu/stm32/eth: Use luid_get_eui48 to generate local, non group EUI
cpu/stm32/eth: Use luid_get_eui48 to generate local, non group EUI

luid_get may generate non compliant EUI (MAC-address) luid_get_eui48
fixes that.

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