cpu/stm43f4: add SRAM based random seed
cpu/stm43f4: add SRAM based random seed

ant9000/RIOT,kbumsik/RIOT,avmelnikoff/RIOT,aeneby/RIOT,miri64/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,x3ro/RIOT,yogo1212/RIOT,kYc0o/RIOT,authmillenon/RIOT,toonst/RIOT,lazytech-org/RIOT,mtausig/RIOT,OTAkeys/RIOT,yogo1212/RIOT,OTAkeys/RIOT,miri64/RIOT,biboc/RIOT,kaspar030/RIOT,kYc0o/RIOT,smlng/RIOT,basilfx/RIOT,mtausig/RIOT,gebart/RIOT,kaspar030/RIOT,BytesGalore/RIOT,yogo1212/RIOT,josephnoir/RIOT,gebart/RIOT,x3ro/RIOT,yogo1212/RIOT,gebart/RIOT,x3ro/RIOT,mfrey/RIOT,basilfx/RIOT,gebart/RIOT,basilfx/RIOT,aeneby/RIOT,aeneby/RIOT,kYc0o/RIOT,x3ro/RIOT,RIOT-OS/RIOT,ant9000/RIOT,kaspar030/RIOT,toonst/RIOT,biboc/RIOT,OTAkeys/RIOT,BytesGalore/RIOT,A-Paul/RIOT,cladmi/RIOT,jasonatran/RIOT,biboc/RIOT,jasonatran/RIOT,cladmi/RIOT,josephnoir/RIOT,gebart/RIOT,rfuentess/RIOT,rfuentess/RIOT,RIOT-OS/RIOT,cladmi/RIOT,avmelnikoff/RIOT,kaspar030/RIOT,cladmi/RIOT,A-Paul/RIOT,mtausig/RIOT,authmillenon/RIOT,miri64/RIOT,authmillenon/RIOT,lazytech-org/RIOT,lazytech-org/RIOT,kbumsik/RIOT,mfrey/RIOT,rfuentess/RIOT,authmillenon/RIOT,avmelnikoff/RIOT,BytesGalore/RIOT,smlng/RIOT,BytesGalore/RIOT,OlegHahm/RIOT,OlegHahm/RIOT,kaspar030/RIOT,OTAkeys/RIOT,A-Paul/RIOT,RIOT-OS/RIOT,aeneby/RIOT,yogo1212/RIOT,smlng/RIOT,jasonatran/RIOT,kYc0o/RIOT,rfuentess/RIOT,x3ro/RIOT,toonst/RIOT,basilfx/RIOT,jasonatran/RIOT,A-Paul/RIOT,aeneby/RIOT,mtausig/RIOT,mfrey/RIOT,avmelnikoff/RIOT,kbumsik/RIOT,lazytech-org/RIOT,ant9000/RIOT,smlng/RIOT,toonst/RIOT,smlng/RIOT,miri64/RIOT,mfrey/RIOT,mtausig/RIOT,josephnoir/RIOT,kbumsik/RIOT,basilfx/RIOT,authmillenon/RIOT,miri64/RIOT,toonst/RIOT,authmillenon/RIOT,ant9000/RIOT,cladmi/RIOT,avmelnikoff/RIOT,ant9000/RIOT,yogo1212/RIOT,lazytech-org/RIOT,RIOT-OS/RIOT,mfrey/RIOT,BytesGalore/RIOT,OlegHahm/RIOT,biboc/RIOT,jasonatran/RIOT,rfuentess/RIOT,A-Paul/RIOT,josephnoir/RIOT,josephnoir/RIOT,kbumsik/RIOT,kYc0o/RIOT,OTAkeys/RIOT,biboc/RIOT,OlegHahm/RIOT