sched/clock: Refine the code structure for userspace access

Reorganize perf_gettime implementation to eliminate duplicate functions
and improve code structure for userspace library integration,
consolidating logic flow for better maintainability.

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

sched/clock/clock_perf.c

@@ -104,28 +104,6 @@ clock_t perf_gettime(void)
   return result;
 }
 
-/****************************************************************************
- * perf_convert
- ****************************************************************************/
-
-void perf_convert(clock_t elapsed, FAR struct timespec *ts)
-{
-  unsigned long freq = up_perf_getfreq();
-
-  ts->tv_sec  = elapsed / freq;
-  elapsed -= ts->tv_sec * freq;
-  ts->tv_nsec = NSEC_PER_SEC * elapsed / freq;
-}
-
-/****************************************************************************
- * perf_getfreq
- ****************************************************************************/
-
-unsigned long perf_getfreq(void)
-{
-  return up_perf_getfreq();
-}
-
 #elif defined(CONFIG_ALARM_ARCH) || defined (CONFIG_TIMER_ARCH) || \
       defined(CONFIG_ARCH_PERF_EVENTS)
 
@@ -138,6 +116,22 @@ clock_t perf_gettime(void)
   return up_perf_gettime();
 }
 
+#else
+
+/****************************************************************************
+ * perf_gettime
+ ****************************************************************************/
+
+clock_t perf_gettime(void)
+{
+  return clock_systime_ticks();
+}
+
+#endif
+
+#if defined(CONFIG_ALARM_ARCH) || defined (CONFIG_TIMER_ARCH) || \
+    defined(CONFIG_ARCH_PERF_EVENTS)
+
 /****************************************************************************
  * perf_convert
  ****************************************************************************/
@@ -158,15 +152,6 @@ unsigned long perf_getfreq(void)
 
 #else
 
-/****************************************************************************
- * perf_gettime
- ****************************************************************************/
-
-clock_t perf_gettime(void)
-{
-  return clock_systime_ticks();
-}
-
 /****************************************************************************
  * perf_convert
  ****************************************************************************/