NFS: Replace old NFSv3 encoder functions with xdr_stream-based ones

The naming scheme of the new encoder functions, which follows the
NFSv4 XDR encoder functions, is slightly different than the scheme
used for the old functions.  Rename the functions as a separate
step to keep the patches clean.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>