cpu/sam0/rtc_rtt: integrate pm_layered
cpu/sam0/rtc_rtt: integrate pm_layered

kaspar030/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,kaspar030/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT