powerpc: Fix compilation for 32-bit configs

Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/include/asm-ppc/pci-bridge.h b/include/asm-ppc/pci-bridge.h
index ffa4234..e58c78f 100644
--- a/include/asm-ppc/pci-bridge.h
+++ b/include/asm-ppc/pci-bridge.h
@@ -79,6 +79,11 @@
 	struct resource mem_space;
 };
 
+static inline struct pci_controller *pci_bus_to_host(struct pci_bus *bus)
+{
+	return bus->sysdata;
+}
+
 /* These are used for config access before all the PCI probing
    has been done. */
 int early_read_config_byte(struct pci_controller *hose, int bus, int dev_fn,