sched/hrtimer: Replace hrtimer_gettime with clock_systime_nsec.

This commit move the hrtimer_gettime to clock_systime_nsec to improve
the code reusability.

Signed-off-by: ouyangxiangzhen <ouyangxiangzhen@xiaomi.com>

include/nuttx/clock.h

@@ -733,6 +733,28 @@ clock_t clock_systime_ticks(void);
 
 void clock_systime_timespec(FAR struct timespec *ts);
 
+/****************************************************************************
+ * Name: clock_systime_nsec
+ *
+ * Description:
+ *   Return the current value of the system timer counter as
+ *   uint64_t nanoseconds.
+ *
+ * Input Parameters:
+ *   ts - Location to return the time
+ *
+ * Returned Value:
+ *   The current system time in nanoseconds.
+ *
+ ****************************************************************************/
+
+static inline_function uint64_t clock_systime_nsec(void)
+{
+  struct timespec ts;
+  clock_systime_timespec(&ts);
+  return clock_time2nsec(&ts);
+}
+
 /****************************************************************************
  * Name:  clock_cpuload
  *

sched/hrtimer/hrtimer.h

@@ -110,30 +110,6 @@ void hrtimer_process(uint64_t now);
  * Inline Functions
  ****************************************************************************/
 
-/****************************************************************************
- * Name: hrtimer_gettime
- *
- * Description:
- *   Get the current high-resolution time in nanoseconds.
- *
- * Returned Value:
- *   Current time in nanoseconds.
- ****************************************************************************/
-
-static inline_function
-uint64_t hrtimer_gettime(void)
-{
-  struct timespec ts;
-
-  /* Get current time from platform-specific timer */
-
-  clock_systime_timespec(&ts);
-
-  /* Convert timespec to nanoseconds */
-
-  return clock_time2nsec(&ts);
-}
-
 /****************************************************************************
  * Name: hrtimer_reprogram
  *

sched/hrtimer/hrtimer_start.c

@@ -92,7 +92,7 @@ int hrtimer_start(FAR hrtimer_t *hrtimer, hrtimer_entry_t func,
     }
   else
     {
-      hrtimer->expired = hrtimer_gettime() + expired;
+      hrtimer->expired = clock_systime_nsec() + expired;
     }
 
   /* Ensure expiration time does not overflow */

sched/sched/sched_timer.c

@@ -135,7 +135,7 @@ void nxsched_process_timer(void)
                     HRTIMER_MODE_REL);
     }
 
-  hrtimer_process(hrtimer_gettime());
+  hrtimer_process(clock_systime_nsec());
 #else
   /* Fallback: process one scheduler tick */