sfc: Do not attempt to flush queues if DMA is disabled

efx_nic_fatal_interrupt() disables DMA before scheduling a reset.
After this, we need not and *cannot* flush queues.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/net/ethernet/sfc/efx.c

@@ -656,12 +656,16 @@ static void efx_stop_datapath(struct efx_nic *efx)
 	struct efx_channel *channel;
 	struct efx_tx_queue *tx_queue;
 	struct efx_rx_queue *rx_queue;
+	struct pci_dev *dev = efx->pci_dev;
 	int rc;
 
 	EFX_ASSERT_RESET_SERIALISED(efx);
 	BUG_ON(efx->port_enabled);
 
+	/* Only perform flush if dma is enabled */
+	if (dev->is_busmaster) {
 		rc = efx_nic_flush_queues(efx);
+
 		if (rc && EFX_WORKAROUND_7803(efx)) {
 			/* Schedule a reset to recover from the flush failure. The
 			 * descriptor caches reference memory we're about to free,
@@ -676,6 +680,7 @@ static void efx_stop_datapath(struct efx_nic *efx)
 			netif_dbg(efx, drv, efx->net_dev,
 				  "successfully flushed all queues\n");
 		}
+	}
 
 	efx_for_each_channel(channel, efx) {
 		/* RX packet processing is pipelined, so wait for the