cpu/atmega256rfr2: configure RAM and ROM length
cpu/atmega256rfr2: configure RAM and ROM length

Info taken from https://www.microchip.com/wwwproducts/en/atmega256rfr2

TODO: update "board not enough memory".

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