pci: fix overflow in __pci_hose_bus_to_phys w/ large RAM

If a 32-bit system has 2GB of RAM, and the base address of that RAM is
2GB, then start+size will overflow a 32-bit value (to a value of 0).

To avoid such an overflow, convert __pci_hose_bus_to_phys() to calculate
the offset of a bus address into a PCI region, rather than comparing a
bus address against the end of a PCI region.

Signed-off-by: Stephen Warren <swarren@nvidia.com>

drivers/pci/pci.c

@@ -323,7 +323,7 @@ int __pci_hose_bus_to_phys(struct pci_controller *hose,
 			continue;
 
 		if (bus_addr >= res->bus_start &&
-			bus_addr < res->bus_start + res->size) {
+			(bus_addr - res->bus_start) < res->size) {
 			*pa = (bus_addr - res->bus_start + res->phys_start);
 			return 0;
 		}