libata: fix build without BMDMA

fix these errors:
drivers/ata/libata-sff.c:2538:3: error: implicit declaration of function
'ata_pci_bmdma_prepare_host'
drivers/ata/libata-sff.c:2549:40: error: 'ata_bmdma_interrupt'
undeclared (first use in this function)

Signed-off-by: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/drivers/ata/libata-sff.c b/drivers/ata/libata-sff.c
index 63d5327..4cadfa2 100644
--- a/drivers/ata/libata-sff.c
+++ b/drivers/ata/libata-sff.c
@@ -2533,10 +2533,12 @@
 	if (rc)
 		goto out;
 
+#ifdef CONFIG_ATA_BMDMA
 	if (bmdma)
 		/* prepare and activate BMDMA host */
 		rc = ata_pci_bmdma_prepare_host(pdev, ppi, &host);
 	else
+#endif
 		/* prepare and activate SFF host */
 		rc = ata_pci_sff_prepare_host(pdev, ppi, &host);
 	if (rc)
@@ -2544,10 +2546,12 @@
 	host->private_data = host_priv;
 	host->flags |= hflags;
 
+#ifdef CONFIG_ATA_BMDMA
 	if (bmdma) {
 		pci_set_master(pdev);
 		rc = ata_pci_sff_activate_host(host, ata_bmdma_interrupt, sht);
 	} else
+#endif
 		rc = ata_pci_sff_activate_host(host, ata_sff_interrupt, sht);
 out:
 	if (rc == 0)