drm/radeon: Fix pci_map_page() error checking

0 is a valid DMA address from pci_map_page(), use pci_dma_mapping_error()
instead to check for errors

[airlied: fix warning + two other places with errors.]
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/ati_pcigart.c

@@ -152,7 +152,7 @@ int drm_ati_pcigart_init(struct drm_device *dev, struct drm_ati_pcigart_info *ga
 		/* we need to support large memory configurations */
 		entry->busaddr[i] = pci_map_page(dev->pdev, entry->pagelist[i],
 						 0, PAGE_SIZE, PCI_DMA_BIDIRECTIONAL);
-		if (entry->busaddr[i] == 0) {
+		if (pci_dma_mapping_error(dev->pdev, entry->busaddr[i])) {
 			DRM_ERROR("unable to map PCIGART pages!\n");
 			drm_ati_pcigart_cleanup(dev, gart_info);
 			address = NULL;

drivers/gpu/drm/radeon/r600_cp.c

@@ -200,7 +200,7 @@ int r600_page_table_init(struct drm_device *dev)
 						 entry->pagelist[i], 0,
 						 PAGE_SIZE,
 						 PCI_DMA_BIDIRECTIONAL);
-		if (entry->busaddr[i] == 0) {
+		if (pci_dma_mapping_error(dev->pdev, entry->busaddr[i])) {
 			DRM_ERROR("unable to map PCIGART pages!\n");
 			r600_page_table_cleanup(dev, gart_info);
 			goto done;

drivers/gpu/drm/radeon/radeon_device.c

@@ -347,7 +347,8 @@ int radeon_dummy_page_init(struct radeon_device *rdev)
 		return -ENOMEM;
 	rdev->dummy_page.addr = pci_map_page(rdev->pdev, rdev->dummy_page.page,
 					0, PAGE_SIZE, PCI_DMA_BIDIRECTIONAL);
-	if (!rdev->dummy_page.addr) {
+	if (pci_dma_mapping_error(rdev->pdev, rdev->dummy_page.addr)) {
+		dev_err(&rdev->pdev->dev, "Failed to DMA MAP the dummy page\n");
 		__free_page(rdev->dummy_page.page);
 		rdev->dummy_page.page = NULL;
 		return -ENOMEM;