sys/puf_sram: extend documentation
sys/puf_sram: extend documentation

miri64/RIOT,OTAkeys/RIOT,smlng/RIOT,x3ro/RIOT,ant9000/RIOT,basilfx/RIOT,OTAkeys/RIOT,authmillenon/RIOT,ant9000/RIOT,authmillenon/RIOT,mtausig/RIOT,x3ro/RIOT,OTAkeys/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,josephnoir/RIOT,josephnoir/RIOT,yogo1212/RIOT,RIOT-OS/RIOT,miri64/RIOT,smlng/RIOT,kaspar030/RIOT,kYc0o/RIOT,x3ro/RIOT,ant9000/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,mtausig/RIOT,toonst/RIOT,OTAkeys/RIOT,kaspar030/RIOT,josephnoir/RIOT,miri64/RIOT,basilfx/RIOT,smlng/RIOT,kYc0o/RIOT,kYc0o/RIOT,ant9000/RIOT,mtausig/RIOT,OlegHahm/RIOT,x3ro/RIOT,toonst/RIOT,toonst/RIOT,jasonatran/RIOT,smlng/RIOT,mtausig/RIOT,josephnoir/RIOT,kaspar030/RIOT,kaspar030/RIOT,miri64/RIOT,toonst/RIOT,yogo1212/RIOT,OlegHahm/RIOT,authmillenon/RIOT,yogo1212/RIOT,x3ro/RIOT,authmillenon/RIOT,yogo1212/RIOT,josephnoir/RIOT,OlegHahm/RIOT,jasonatran/RIOT,basilfx/RIOT,authmillenon/RIOT,yogo1212/RIOT,basilfx/RIOT,toonst/RIOT,kaspar030/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,mtausig/RIOT,kYc0o/RIOT,miri64/RIOT,yogo1212/RIOT,OlegHahm/RIOT,ant9000/RIOT,authmillenon/RIOT,smlng/RIOT,RIOT-OS/RIOT,basilfx/RIOT