powerpc/iseries: Fix possible null pointer dereference in iSeries_pcibios_fixup_resources

I don't know if this is a right fix for the problem
since of_get_property can return NULL.
Since iseries_device_information is used only for informational purpose,
we can skip this function without valid HvSubBusNumber number.
Signed-off-by: Denis Kirjanov <dkirjanov@kernel.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/iseries/pci.c

@@ -445,7 +445,11 @@ void __init iSeries_pcibios_fixup_resources(struct pci_dev *pdev)
 	}
 
 	allocate_device_bars(pdev);
+	if (likely(sub_bus))
 		iseries_device_information(pdev, bus, *sub_bus);
+	else
+		printk(KERN_ERR "PCI: Device node %s has missing or invalid "
+				"linux,subbus property\n", node->full_name);
 }
 
 /*