cpu/fe310: Add architecture_arch.h
cpu/fe310: Add architecture_arch.h

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