timekeeping: Remove TK_MIRROR timekeeping_update() action

All call sites of using TK_MIRROR flag in timekeeping_update() are
gone. The TK_MIRROR dependent code path is therefore dead code.

Remove it along with the TK_MIRROR define.

Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-24-554456a44a15@linutronix.de

kernel/time/timekeeping.c

@@ -30,8 +30,7 @@
 #include "timekeeping_internal.h"
 
 #define TK_CLEAR_NTP		(1 << 0)
-#define TK_MIRROR		(1 << 1)
-#define TK_CLOCK_WAS_SET	(1 << 2)
+#define TK_CLOCK_WAS_SET	(1 << 1)
 
 #define TK_UPDATE_ALL		(TK_CLEAR_NTP | TK_CLOCK_WAS_SET)
 
@@ -816,13 +815,6 @@ static void timekeeping_update(struct tk_data *tkd, struct timekeeper *tk, unsig
 
 	if (action & TK_CLOCK_WAS_SET)
 		tk->clock_was_set_seq++;
-	/*
-	 * The mirroring of the data to the shadow-timekeeper needs
-	 * to happen last here to ensure we don't over-write the
-	 * timekeeper structure on the next update with stale data
-	 */
-	if (action & TK_MIRROR)
-		timekeeping_restore_shadow(tkd);
 }
 
 static void timekeeping_update_from_shadow(struct tk_data *tkd, unsigned int action)