[PATCH] fix nfsacl pointer arithmetic and pg_class initialization bugs

* Pointer arithmetic bug: p is in word units. This fixes a memory
  corruption with big acls.
* Initialize pg_class to prevent a NULL pointer access.

Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>