nfsd4: generic callback code

Make the recall callback code more generic, so that other callbacks
will be able to use it too.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index f988b90..6e59214 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -72,6 +72,8 @@
 
 struct nfsd4_callback {
 	struct nfsd4_cb_args cb_args;
+	struct rpc_message cb_msg;
+	const struct rpc_call_ops *cb_ops;
 	struct work_struct cb_work;
 };