PCI: add generic pcibios_resource_to_bus()

This replaces the generic versions of pcibios_resource_to_bus() and
pcibios_bus_to_resource() in asm-generic/pci.h with versions that use
pci_resource_to_bus() and pci_bus_to_resource().

The replacements are equivalent except that they can apply host
bridge window offsets when the arch has supplied them by using
pci_add_resource_offset().

Each arch can convert to using pci_add_resource_offset() individually by
removing its device resource fixups from pcibios_fixup_bus() and supplying
ARCH_HAS_GENERIC_PCI_OFFSETS.  ARCH_HAS_GENERIC_PCI_OFFSETS can be removed
after all have converted.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 419f78f9..be58a51 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -648,6 +648,10 @@
 
 /* Generic PCI functions used internally */
 
+void pcibios_resource_to_bus(struct pci_dev *dev, struct pci_bus_region *region,
+			     struct resource *res);
+void pcibios_bus_to_resource(struct pci_dev *dev, struct resource *res,
+			     struct pci_bus_region *region);
 void pcibios_scan_specific_bus(int busn);
 extern struct pci_bus *pci_find_bus(int domain, int busnr);
 void pci_bus_add_devices(const struct pci_bus *bus);