timekeeping: Reuse timekeeping_cycles_to_ns()

Simplify __timekeeping_get_ns() by reusing timekeeping_cycles_to_ns().

No functional change.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240325064023.2997-13-adrian.hunter@intel.com

kernel/time/timekeeping.c

@@ -391,10 +391,7 @@ static inline u64 timekeeping_cycles_to_ns(const struct tk_read_base *tkr, u64 c
 
 static __always_inline u64 __timekeeping_get_ns(const struct tk_read_base *tkr)
 {
-	u64 delta, cycles = tk_clock_read(tkr);
-
-	delta = clocksource_delta(cycles, tkr->cycle_last, tkr->mask);
-	return timekeeping_delta_to_ns(tkr, delta);
+	return timekeeping_cycles_to_ns(tkr, tk_clock_read(tkr));
 }
 
 static inline u64 timekeeping_get_ns(const struct tk_read_base *tkr)