System lib: Remove unused variable from CPU load tracking

src/modules/systemlib/cpuload.c

@@ -78,8 +78,6 @@ void cpuload_initialize_once()
 		system_load.tasks[i].valid = false;
 	}
 
-	uint64_t now = hrt_absolute_time();
-
 	int static_tasks_count = 2;	// there are at least 2 threads that should be initialized statically - "idle" and "init"
 
 #ifdef CONFIG_PAGING
@@ -94,7 +92,6 @@ void cpuload_initialize_once()
 
 	// perform static initialization of "system" threads
 	for (system_load.total_count = 0; system_load.total_count < static_tasks_count; system_load.total_count++) {
-		system_load.tasks[system_load.total_count].start_time = now;
 		system_load.tasks[system_load.total_count].total_runtime = 0;
 		system_load.tasks[system_load.total_count].curr_start_time = 0;
 		system_load.tasks[system_load.total_count].tcb = sched_gettcb(
@@ -111,7 +108,6 @@ void sched_note_start(FAR struct tcb_s *tcb)
 	for (i = 1; i < CONFIG_MAX_TASKS; i++) {
 		if (!system_load.tasks[i].valid) {
 			/* slot is available */
-			system_load.tasks[i].start_time = hrt_absolute_time();
 			system_load.tasks[i].total_runtime = 0;
 			system_load.tasks[i].curr_start_time = 0;
 			system_load.tasks[i].tcb = tcb;

src/modules/systemlib/cpuload.h

@@ -42,7 +42,6 @@ __BEGIN_DECLS
 struct system_load_taskinfo_s {
 	uint64_t total_runtime;			///< Runtime since start (start_time - total_runtime)/(start_time - current_time) = load
 	uint64_t curr_start_time;		///< Start time of the current scheduling slot
-	uint64_t start_time;			///< FIRST start time of task
 	FAR struct tcb_s *tcb;			///<
 	bool valid;						///< Task is currently active / valid
 };