net: ravb: Align poll function with NAPI docs

Align ravb_poll() with the documentation in
`Documentation/networking/kapi.rst` and
`Documentation/networking/napi.rst`.

The documentation says that we should prefer napi_complete_done() over
napi_complete(), and using the former allows us to properly support busy
polling. We should ensure that napi_complete_done() is only called if
the work budget has not been exhausted, and we should only re-arm
interrupts if it returns true.
Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/renesas/ravb_main.c

@@ -1341,11 +1341,7 @@ static int ravb_poll(struct napi_struct *napi, int budget)
 	if (priv->rx_fifo_errors != ndev->stats.rx_fifo_errors)
 		ndev->stats.rx_fifo_errors = priv->rx_fifo_errors;
 
-	if (work_done == budget)
-		goto out;
-
-	napi_complete(napi);
-
+	if (work_done < budget && napi_complete_done(napi, work_done)) {
 		/* Re-enable RX/TX interrupts */
 		spin_lock_irqsave(&priv->lock, flags);
 		if (!info->irq_en_dis) {
@@ -1356,8 +1352,8 @@ static int ravb_poll(struct napi_struct *napi, int budget)
 			ravb_write(ndev, mask, TIE);
 		}
 		spin_unlock_irqrestore(&priv->lock, flags);
+	}
 
-out:
 	return work_done;
 }