setfacl fails with older kernels (4.x 3.x)

Module includes all required function definitions to build with ACL support on older kernels but attempting to set acl information fails with:

```
setfacl -m u:root:r /mnt/file
setfacl: /mnt/file: Operation not supported
```

Probably a few things are missing here which are handled by the `generic_acl_access_handler` functions exported
by newer kernel versions. I could not make it work, help welcome (if required)