PCI: OF: Initialize dev->fwnode appropriately

For PCI devices that have an OF node, set the fwnode as well. This way
drivers that rely on fwnode don't need the special case described by
commit f94277af ("of/platform: Initialise dev->fwnode appropriately").

Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>