Revert "NFSD: Convert the callback workqueue to use delayed_work"

This commit was a pre-requisite for commit c1ccfcf1 ("NFSD:
Reschedule CB operations when backchannel rpc_clnt is shut down"),
which has already been reverted.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4callback.c

@@ -983,7 +983,7 @@ static struct workqueue_struct *callback_wq;
 static bool nfsd4_queue_cb(struct nfsd4_callback *cb)
 {
 	trace_nfsd_cb_queue(cb->cb_clp, cb);
-	return queue_delayed_work(callback_wq, &cb->cb_work, 0);
+	return queue_work(callback_wq, &cb->cb_work);
 }
 
 static void nfsd41_cb_inflight_begin(struct nfs4_client *clp)
@@ -1482,7 +1482,7 @@ static void
 nfsd4_run_cb_work(struct work_struct *work)
 {
 	struct nfsd4_callback *cb =
-		container_of(work, struct nfsd4_callback, cb_work.work);
+		container_of(work, struct nfsd4_callback, cb_work);
 	struct nfs4_client *clp = cb->cb_clp;
 	struct rpc_clnt *clnt;
 	int flags;
@@ -1528,7 +1528,7 @@ void nfsd4_init_cb(struct nfsd4_callback *cb, struct nfs4_client *clp,
 	cb->cb_msg.rpc_argp = cb;
 	cb->cb_msg.rpc_resp = cb;
 	cb->cb_ops = ops;
-	INIT_DELAYED_WORK(&cb->cb_work, nfsd4_run_cb_work);
+	INIT_WORK(&cb->cb_work, nfsd4_run_cb_work);
 	cb->cb_status = 0;
 	cb->cb_need_restart = false;
 	cb->cb_holds_slot = false;

fs/nfsd/state.h

@@ -68,7 +68,7 @@ struct nfsd4_callback {
 	struct nfs4_client *cb_clp;
 	struct rpc_message cb_msg;
 	const struct nfsd4_callback_ops *cb_ops;
-	struct delayed_work cb_work;
+	struct work_struct cb_work;
 	int cb_seq_status;
 	int cb_status;
 	bool cb_need_restart;