dm: pci: Use a 1:1 mapping for bus <-> phy addresses

If U-Boot gets used as coreboot payload all pci resources got
assigned by coreboot. If a dts without any pci ranges gets used
the dm is not able to access pci device memory. To get things
working make use of a 1:1 mapping for bus <-> phy addresses.

This change makes it possible to get the e1000 U-Boot driver
working on a sandybridge device where U-Boot is used as coreboot
payload.

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
[bmeng: fixed 'u-boot' in the commit message]
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/pci/pci-uclass.c

@@ -1182,6 +1182,11 @@ static int _dm_pci_bus_to_phys(struct udevice *ctlr,
 	struct pci_region *res;
 	int i;
 
+	if (hose->region_count == 0) {
+		*pa = bus_addr;
+		return 0;
+	}
+
 	for (i = 0; i < hose->region_count; i++) {
 		res = &hose->regions[i];
 
@@ -1245,6 +1250,11 @@ int _dm_pci_phys_to_bus(struct udevice *dev, phys_addr_t phys_addr,
 	ctlr = pci_get_controller(dev);
 	hose = dev_get_uclass_priv(ctlr);
 
+	if (hose->region_count == 0) {
+		*ba = phys_addr;
+		return 0;
+	}
+
 	for (i = 0; i < hose->region_count; i++) {
 		res = &hose->regions[i];