sys/ztimer/Kconfig: remv dep between ztimer64_compat and ztimer_compat
sys/ztimer/Kconfig: remv dep between ztimer64_compat and ztimer_compat

This is done to avoid circular dependency, it will currently allow for
ztimer64_xtimer_compat beeing selected as well as xtimer_on_ztimer.
This altough incorrect mimics make, and will be fixed when making
ztimer_xtimer_compat the default xtimer backend

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