powerpc/pci: Add pci_find_controller_for_domain()

Add a helper to find the pci_controller structure based on the domain
number / phb id.
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Reviewed-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/pci-bridge.h

@@ -273,6 +273,8 @@ extern int pcibios_map_io_space(struct pci_bus *bus);
 extern struct pci_controller *pci_find_hose_for_OF_device(
 			struct device_node* node);
 
+extern struct pci_controller *pci_find_controller_for_domain(int domain_nr);
+
 /* Fill up host controller resources from the OF node */
 extern void pci_process_bridge_OF_ranges(struct pci_controller *hose,
 			struct device_node *dev, int primary);

arch/powerpc/kernel/pci-common.c

@@ -351,6 +351,17 @@ struct pci_controller* pci_find_hose_for_OF_device(struct device_node* node)
 	return NULL;
 }
 
+struct pci_controller *pci_find_controller_for_domain(int domain_nr)
+{
+	struct pci_controller *hose;
+
+	list_for_each_entry(hose, &hose_list, list_node)
+		if (hose->global_number == domain_nr)
+			return hose;
+
+	return NULL;
+}
+
 /*
  * Reads the interrupt pin to determine if interrupt is use by card.
  * If the interrupt is used, then gets the interrupt line from the