microblaze/PCI: fix "io_offset undeclared" error

There is a compile error for microblaze pci because io_offset is not
declared. This patch adds declaration of io_offset.

[bhelgaas: I introduced this problem with 58de74b8053]
Signed-off-by: Hiroo MATSUMOTO <matsumoto.hiroo@jp.fujitsu.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/arch/microblaze/pci/pci-common.c b/arch/microblaze/pci/pci-common.c
index d10403d..ed22bfc 100644
--- a/arch/microblaze/pci/pci-common.c
+++ b/arch/microblaze/pci/pci-common.c
@@ -1422,6 +1422,7 @@
 
 static void __devinit pcibios_setup_phb_resources(struct pci_controller *hose, struct list_head *resources)
 {
+	unsigned long io_offset;
 	struct resource *res;
 	int i;