rbd: use KMEM_CACHE macro

Use KMEM_CACHE() instead of kmem_cache_create() to simplify the code.
Signed-off-by: NGeliang Tang <geliangtang@163.com>
Signed-off-by: NIlya Dryomov <idryomov@gmail.com>

drivers/block/rbd.c

@@ -5641,18 +5641,12 @@ static void rbd_sysfs_cleanup(void)
 static int rbd_slab_init(void)
 {
 	rbd_assert(!rbd_img_request_cache);
-	rbd_img_request_cache = kmem_cache_create("rbd_img_request",
-					sizeof (struct rbd_img_request),
-					__alignof__(struct rbd_img_request),
-					0, NULL);
+	rbd_img_request_cache = KMEM_CACHE(rbd_img_request, 0);
 	if (!rbd_img_request_cache)
 		return -ENOMEM;
 
 	rbd_assert(!rbd_obj_request_cache);
-	rbd_obj_request_cache = kmem_cache_create("rbd_obj_request",
-					sizeof (struct rbd_obj_request),
-					__alignof__(struct rbd_obj_request),
-					0, NULL);
+	rbd_obj_request_cache = KMEM_CACHE(rbd_obj_request, 0);
 	if (!rbd_obj_request_cache)
 		goto out_err;