ARM64: PCI: Add acpi_pci_bus_find_domain_nr()

Extend pci_bus_find_domain_nr() so it can find the domain from either:

  - ACPI, via the new acpi_pci_bus_find_domain_nr() interface, or
  - DT, via of_pci_bus_find_domain_nr()

Note that this is only used for CONFIG_PCI_DOMAINS_GENERIC=y, so it does
not affect x86 or ia64.

[bhelgaas: changelog]
Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 48839e8..0671e9a 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1390,6 +1390,12 @@
 {
 	return bus->domain_nr;
 }
+#ifdef CONFIG_ACPI
+int acpi_pci_bus_find_domain_nr(struct pci_bus *bus);
+#else
+static inline int acpi_pci_bus_find_domain_nr(struct pci_bus *bus)
+{ return 0; }
+#endif
 int pci_bus_find_domain_nr(struct pci_bus *bus, struct device *parent);
 #endif