NFS: fs/nfs/dir.c should #include "internal.h"

Every file should include the headers containing the prototypes for its global
functions (in this case nfs_access_cache_shrinker()).

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>