slub: Fix a typo in config name

There's no config named SLAB_DEBUG, and it should be a typo
of SLUB_DEBUG.
Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

mm/slub.c

@@ -3203,7 +3203,7 @@ static void __init kmem_cache_bootstrap_fixup(struct kmem_cache *s)
 			list_for_each_entry(p, &n->partial, lru)
 				p->slab = s;
 
-#ifdef CONFIG_SLAB_DEBUG
+#ifdef CONFIG_SLUB_DEBUG
 			list_for_each_entry(p, &n->full, lru)
 				p->slab = s;
 #endif