libata-sff; Unbreak non DMA capable controllers again

Seems nobody else is checking/testing this case as it keeps getting
horked.

If we have no BAR4 mapping on an SFF controller this is *NOT* an error,
it just means it isn't doing BMDMA.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/ata/libata-sff.c

@@ -573,6 +573,10 @@ int ata_pci_init_bmdma(struct ata_host *host)
 	struct pci_dev *pdev = to_pci_dev(gdev);
 	int i, rc;
 
+	/* No BAR4 allocation: No DMA */
+	if (pci_resource_start(pdev, 4) == 0)
+		return 0;
+
 	/* TODO: If we get no DMA mask we should fall back to PIO */
 	rc = pci_set_dma_mask(pdev, ATA_DMA_MASK);
 	if (rc)