pci_read_devaddr() is only used by the legacy functions for the old PCI
hotplug interface in pci-hotplug-old.c.  So we move the function there,
and make it static.
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>