slqb: use correct name for rcu callback

struct slqb_page defines struct rcu_head rcu_head for rcu,
the rcu callback should use it.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

mm/slqb.c

@@ -1022,7 +1022,7 @@ static void rcu_free_slab(struct rcu_head *h)
 {
 	struct slqb_page *page;
 
-	page = container_of((struct list_head *)h, struct slqb_page, lru);
+	page = container_of(h, struct slqb_page, rcu_head);
 	__free_slab(page->list->cache, page);
 }