mm: kmemleak: use mem_pool_free() to free object

The kmemleak object is allocated by mem_pool_alloc(), which could be from
slab or mem_pool[], so it's not suitable using __kmem_cache_free() to free
the object, use __mem_pool_free() instead.

Link: https://lkml.kernel.org/r/20231018102952.3339837-6-liushixin2@huawei.com
Fixes: 0647398a

 ("mm: kmemleak: simple memory allocation pool for kmemleak objects")
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Patrick Wang <patrick.wang.shcn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>