mm/mempool: Initialize spinlock with spin_initialize

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

mm/mempool/mempool.c

@@ -206,7 +206,7 @@ int mempool_init(FAR struct mempool_s *pool, FAR const char *name)
       kasan_poison(base, size);
     }
 
-  pool->lock = 0;
+  spin_initialize(&pool->lock, 0);
   if (pool->wait && pool->expandsize == 0)
     {
       nxsem_init(&pool->waitsem, 0, 0);