NFS: readdir shouldn't read beyond the reply returned by the server

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --cc fs/nfs/dir.c
Simple merge

diff --cc fs/nfs/nfs2xdr.c
Simple merge

diff --cc fs/nfs/nfs3xdr.c
Simple merge

diff --cc fs/nfs/nfs4proc.c
Simple merge

diff --cc fs/nfs/nfs4xdr.c
Simple merge