timedated: make ntp_synced() static

No need to have this in basic.

src/basic/time-util.c

@@ -7,7 +7,6 @@
 #include <sys/mman.h>
 #include <sys/time.h>
 #include <sys/timerfd.h>
-#include <sys/timex.h>
 #include <sys/types.h>
 #include <unistd.h>
 
@@ -1245,21 +1244,6 @@ int parse_nsec(const char *t, nsec_t *nsec) {
         return 0;
 }
 
-bool ntp_synced(void) {
-        struct timex txc = {};
-
-        if (adjtimex(&txc) < 0)
-                return false;
-
-        /* Consider the system clock synchronized if the reported maximum error is smaller than the maximum
-         * value (16 seconds). Ignore the STA_UNSYNC flag as it may have been set to prevent the kernel from
-         * touching the RTC. */
-        if (txc.maxerror >= 16000000)
-                return false;
-
-        return true;
-}
-
 int get_timezones(char ***ret) {
         _cleanup_fclose_ FILE *f = NULL;
         _cleanup_strv_free_ char **zones = NULL;