NFS: Create a free_client rpc_op

NFS v4 needs a way to shut down callbacks and sessions, but v2 and v3
don't.

Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 18f99ef..93b7325 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -151,6 +151,7 @@
 
 extern void nfs_cleanup_cb_ident_idr(struct net *);
 extern void nfs_put_client(struct nfs_client *);
+extern void nfs_free_client(struct nfs_client *);
 extern struct nfs_client *nfs4_find_client_ident(struct net *, int);
 extern struct nfs_client *
 nfs4_find_client_sessionid(struct net *, const struct sockaddr *,