PCI: Factor DT-specific pci_bus_find_domain_nr() code out

BugLink: https://bugs.launchpad.net/bugs/1797092

pci_bus_find_domain_nr() retrieves the host bridge domain number in a
DT-specific way.  Rename it to of_pci_bus_find_domain_nr() to reflect that,
so we can add a corresponding function for ACPI.

[bhelgaas: changelog]
Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
(cherry picked from commit 1a4f93f7)
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/pci/pci.c

@@ -4888,7 +4888,7 @@ int pci_get_new_domain_nr(void)
 }
 
 #ifdef CONFIG_PCI_DOMAINS_GENERIC
-int pci_bus_find_domain_nr(struct pci_bus *bus, struct device *parent)
+static int of_pci_bus_find_domain_nr(struct device *parent)
 {
 	static int use_dt_domains = -1;
 	int domain = -1;
@@ -4934,6 +4934,11 @@ int pci_bus_find_domain_nr(struct pci_bus *bus, struct device *parent)
 
 	return domain;
 }
+
+int pci_bus_find_domain_nr(struct pci_bus *bus, struct device *parent)
+{
+	return of_pci_bus_find_domain_nr(parent);
+}
 #endif
 #endif