ext4: Free ext4_prealloc_space using kmem_cache_free

We should use kmem_cache_free to free memory allocated
via kmem_cache_alloc
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/mballoc.c

@@ -2568,7 +2568,7 @@ static void ext4_mb_cleanup_pa(struct ext4_group_info *grp)
 		pa = list_entry(cur, struct ext4_prealloc_space, pa_group_list);
 		list_del(&pa->pa_group_list);
 		count++;
-		kfree(pa);
+		kmem_cache_free(ext4_pspace_cachep, pa);
 	}
 	if (count)
 		mb_debug("mballoc: %u PAs left\n", count);