NFS: Switch in new NFSv3 decoder functions

The naming scheme of the new decoder functions, which follows the
NFSv4 XDR decoder 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>