nfs: remove dead code from nfs_encode_fh()

This code can never be used as the IS_AUTOMOUNT(inode)
case has already been handled.
So remove it to avoid confusion.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>