sched: add init_idle_bootup_task()

add the init_idle_bootup_task() callback to the bootup thread,
unused at the moment. (CFS will use it to switch the scheduling
class of the boot thread to the idle class)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4b912e7..61a111f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -195,6 +195,7 @@
 extern void sched_init(void);
 extern void sched_init_smp(void);
 extern void init_idle(struct task_struct *idle, int cpu);
+extern void init_idle_bootup_task(struct task_struct *idle);
 
 extern cpumask_t nohz_cpu_mask;
 #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ)