set_timer: Start timer when runnable thread count is bigger than one

Change-Id: Ie32799fff2936ffc057f166db5681edccdbf5920

kernel/syscall.c

@@ -7050,7 +7050,7 @@ SYSCALL_DECLARE(setitimer)
 			timer_start = 0;
 	}
 	thread->itimer_enabled = timer_start;
-	set_timer();
+	set_timer(0);
 	return 0;
 }
 
@@ -9499,7 +9499,7 @@ set_cputime(int mode)
 			   thread->itimer_prof.it_value.tv_sec == 0 &&
 			   thread->itimer_prof.it_value.tv_usec == 0){
 				thread->itimer_enabled = 0;
-				set_timer();
+				set_timer(0);
 			}
 		}
 	}