Revert "block: add __init to elv_register"

This reverts commit b5097e956a4d2919ee248d6481e4204c5568ed5c.

The original commit is buggy, we do use the registration functions
at runtime, for instance when loading IO schedulers through sysfs.

Reported-by: Damien Wyart <damien.wyart@gmail.com>
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index e2a6bd7..45a9147 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -143,7 +143,7 @@
  * io scheduler registration
  */
 extern void __init load_default_elevator_module(void);
-extern int __init elv_register(struct elevator_type *);
+extern int elv_register(struct elevator_type *);
 extern void elv_unregister(struct elevator_type *);
 
 /*