lantiq: fix pci with kernel 4.9

Commit 23dac14d058f ("MIPS: PCI: Use struct list_head lists") changed
the controller list from reverse to straight order. Use the last entry
in the controller list to get the fist conroller of the system.

Signed-off-by: Mathias Kresin <dev@kresin.me>

target/linux/lantiq/patches-4.9/0001-MIPS-lantiq-add-pcie-driver.patch

@@ -4143,7 +4143,7 @@ Signed-off-by: John Crispin <blogic@openwrt.org>
 +
 --- a/arch/mips/pci/pci-legacy.c
 +++ b/arch/mips/pci/pci-legacy.c
-@@ -300,3 +300,30 @@ char *__init pcibios_setup(char *str)
+@@ -300,3 +300,31 @@ char *__init pcibios_setup(char *str)
  		return pcibios_plat_setup(str);
  	return str;
  }
@@ -4164,7 +4164,8 @@ Signed-off-by: John Crispin <blogic@openwrt.org>
 +    int bus_nr = 0;
 +    struct pci_controller *hose;
 +
-+    hose = list_first_entry_or_null(&controllers, struct pci_controller, list);
++    if (!list_empty(&controllers))
++        hose = list_last_entry(&controllers, struct pci_controller, list);
 +
 +    if (hose != NULL) {
 +        if (hose->bus != NULL) {