PCI: Rename of_pci_get_host_bridge_resources() device node parameter

We will add a "struct device *dev" parameter to this function soon, so
rename the existing "struct device_node *dev" parameter to "dev_node".

Tested-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>