of/pci: move of_irq_map_pci() into generic code

There is a tiny difference between PPC32 and PPC64. Microblaze uses the
PPC32 variant.

Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
[grant.likely@secretlab.ca: Added comment to #endif, moved documentation
	block to function implementation, fixed for non ppc and microblaze
	compiles]
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/arch/powerpc/include/asm/pci-bridge.h b/arch/powerpc/include/asm/pci-bridge.h
index 51e9e6f..edeb80f 100644
--- a/arch/powerpc/include/asm/pci-bridge.h
+++ b/arch/powerpc/include/asm/pci-bridge.h
@@ -171,6 +171,16 @@
 	return bus->sysdata;
 }
 
+static inline struct device_node *pci_bus_to_OF_node(struct pci_bus *bus)
+{
+	struct pci_controller *host;
+
+	if (bus->self)
+		return pci_device_to_OF_node(bus->self);
+	host = pci_bus_to_host(bus);
+	return host ? host->dn : NULL;
+}
+
 static inline int isa_vaddr_is_ioport(void __iomem *address)
 {
 	/* No specific ISA handling on ppc32 at this stage, it