ANDROID: Export some scheduler APIs for vendor modules

Make some scheduler APIs exports to allow vendor
modules to use them. It is necessary for the modules
to migrate tasks as they want.

  activate_task:
    To make an inactive and migrated task runnable.

  deactivate_task:
    To make an active task migratible.

  check_preempt_curr:
    To check whether a migrated task needs to preempt
    current task and if so, to do it.

  set_task_cpu:
    To set a cpu for a migratible task and force
    the task to be migrated.

  stop_one_cpu_nowait:
    To move a queued task, stopper should be used.

Bug: 155241766

Signed-off-by: Choonghoon Park <choong.park@samsung.com>
Change-Id: Ied940640525101efbbcef6eca0c39f15eb580007

kernel/stop_machine.c

@@ -370,6 +370,7 @@ bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
 	*work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, };
 	return cpu_stop_queue_work(cpu, work_buf);
 }
+EXPORT_SYMBOL_GPL(stop_one_cpu_nowait);
 
 static bool queue_stop_cpus_work(const struct cpumask *cpumask,
 				 cpu_stop_fn_t fn, void *arg,