I/OAT: fail initialization on zero channels detection

On some systems with I/OAT ver.2 when DCA is disabled in BIOS
situations have been observed
that zero DMA channels are detected instead of four.
To avoid kernel panic driver should fail gracefully with appropriate message.
Signed-off-by: NMaciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: NShannon Nelson <shannon.nelson@intel.com>
Acked-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

drivers/dma/ioat_dma.c

@@ -1659,6 +1659,13 @@ struct ioatdma_device *ioat_dma_probe(struct pci_dev *pdev,
 		" %d channels, device version 0x%02x, driver version %s\n",
 		device->common.chancnt, device->version, IOAT_DMA_VERSION);
 
+	if (!device->common.chancnt) {
+		dev_err(&device->pdev->dev,
+			"Intel(R) I/OAT DMA Engine problem found: "
+			"zero channels detected\n");
+		goto err_setup_interrupts;
+	}
+
 	err = ioat_dma_setup_interrupts(device);
 	if (err)
 		goto err_setup_interrupts;