mm: Enable SLUB for RT

Make SLUB RT aware by converting locks to raw and using free lists to
move the freeing out of the lock held region.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/mm/slab.h b/mm/slab.h
index bc05fdc..610cf61 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -426,7 +426,11 @@
  * The slab lists for all objects.
  */
 struct kmem_cache_node {
+#ifdef CONFIG_SLUB
+	raw_spinlock_t list_lock;
+#else
 	spinlock_t list_lock;
+#endif
 
 #ifdef CONFIG_SLAB
 	struct list_head slabs_partial;	/* partial list first, better asm code */