pkg/littlefs: hook up vfs_fsync()
pkg/littlefs: hook up vfs_fsync()

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