PCI: Add "weak" generic pcibios_enable_device() implementation

Many architectures implement pcibios_enable_device() the same way, so
provide a default implementation in the core.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pci.c

@@ -1185,6 +1185,11 @@ int pci_load_and_free_saved_state(struct pci_dev *dev,
 }
 EXPORT_SYMBOL_GPL(pci_load_and_free_saved_state);
 
+int __weak pcibios_enable_device(struct pci_dev *dev, int bars)
+{
+	return pci_enable_resources(dev, bars);
+}
+
 static int do_pci_enable_device(struct pci_dev *dev, int bars)
 {
 	int err;