Fix undefined reference to `register_task_migration_notifier'

-ck

---
 kernel/sched/bfs.c |    7 +++++++
 1 file changed, 7 insertions(+)

Index: linux-4.0.2-ck1/kernel/sched/bfs.c
===================================================================
--- linux-4.0.2-ck1.orig/kernel/sched/bfs.c	2015-05-08 09:03:55.730280539 +1000
+++ linux-4.0.2-ck1/kernel/sched/bfs.c	2015-05-08 09:18:42.266015120 +1000
@@ -976,6 +976,13 @@ static inline void deactivate_task(struc
 	clear_sticky(p);
 }
 
+static ATOMIC_NOTIFIER_HEAD(task_migration_notifier);
+
+void register_task_migration_notifier(struct notifier_block *n)
+{
+	atomic_notifier_chain_register(&task_migration_notifier, n);
+}
+
 #ifdef CONFIG_SMP
 void set_task_cpu(struct task_struct *p, unsigned int cpu)
 {