timekeeping: Fix references to nonexistent ktime_get_fast_ns()

There was never a function named ktime_get_fast_ns().
Presumably these should refer to ktime_get_mono_fast_ns() instead.

Fixes: c1ce406e ("timekeeping: Fix up function documentation for the NMI safe accessors")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/r/06df7b3cbd94f016403bbf6cd2b38e4368e7468f.1682516546.git.geert+renesas@glider.be

kernel/time/timekeeping.c

@@ -526,7 +526,7 @@ EXPORT_SYMBOL_GPL(ktime_get_raw_fast_ns);
  * partially updated.  Since the tk->offs_boot update is a rare event, this
  * should be a rare occurrence which postprocessing should be able to handle.
  *
- * The caveats vs. timestamp ordering as documented for ktime_get_fast_ns()
+ * The caveats vs. timestamp ordering as documented for ktime_get_mono_fast_ns()
  * apply as well.
  */
 u64 notrace ktime_get_boot_fast_ns(void)
@@ -576,7 +576,7 @@ static __always_inline u64 __ktime_get_real_fast(struct tk_fast *tkf, u64 *mono)
 /**
  * ktime_get_real_fast_ns: - NMI safe and fast access to clock realtime.
  *
- * See ktime_get_fast_ns() for documentation of the time stamp ordering.
+ * See ktime_get_mono_fast_ns() for documentation of the time stamp ordering.
  */
 u64 ktime_get_real_fast_ns(void)
 {