timekeeping: Remove CONFIG_DEBUG_TIMEKEEPING

Since 135225a363 timekeeping_cycles_to_ns() handles large offsets which
would lead to 64bit multiplication overflows correctly. It's also protected
against negative motion of the clocksource unconditionally, which was
exclusive to x86 before.

timekeeping_advance() handles large offsets already correctly.

That means the value of CONFIG_DEBUG_TIMEKEEPING which analyzed these cases
is very close to zero. Remove all of it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241031120328.536010148@linutronix.de

include/linux/timekeeper_internal.h

@@ -76,9 +76,6 @@ struct tk_read_base {
  *				ntp shifted nano seconds.
  * @ntp_err_mult:		Multiplication factor for scaled math conversion
  * @skip_second_overflow:	Flag used to avoid updating NTP twice with same second
- * @last_warning:		Warning ratelimiter (DEBUG_TIMEKEEPING)
- * @underflow_seen:		Underflow warning flag (DEBUG_TIMEKEEPING)
- * @overflow_seen:		Overflow warning flag (DEBUG_TIMEKEEPING)
  *
  * Note: For timespec(64) based interfaces wall_to_monotonic is what
  * we need to add to xtime (or xtime corrected for sub jiffy times)
@@ -147,19 +144,6 @@ struct timekeeper {
 	u32			ntp_error_shift;
 	u32			ntp_err_mult;
 	u32			skip_second_overflow;
-
-#ifdef CONFIG_DEBUG_TIMEKEEPING
-	long			last_warning;
-	/*
-	 * These simple flag variables are managed
-	 * without locks, which is racy, but they are
-	 * ok since we don't really care about being
-	 * super precise about how many events were
-	 * seen, just that a problem was observed.
-	 */
-	int			underflow_seen;
-	int			overflow_seen;
-#endif
 };
 
 #ifdef CONFIG_GENERIC_TIME_VSYSCALL