timekeeping: Add missing parameter documentation for update_fast_time…

…keeper()

Address the following warning:

 kernel/time/timekeeping.c:415: warning: Function parameter or member
 'tkf' not described in 'update_fast_timekeeper'

[ tglx: Remove the bogus ktime_get_mono_fast_ns() part ]

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/1605252275-63652-2-git-send-email-alex.shi@linux.alibaba.com

kernel/time/timekeeping.c

@@ -407,6 +407,7 @@ static inline u64 timekeeping_cycles_to_ns(const struct tk_read_base *tkr, u64 c
 /**
  * update_fast_timekeeper - Update the fast and NMI safe monotonic timekeeper.
  * @tkr: Timekeeping readout base from which we take the update
+ * @tkf: Pointer to NMI safe timekeeper
  *
  * We want to use this from any context including NMI and tracing /
  * instrumenting the timekeeping code itself.