PCI: fix pci_setup_device()'s sprinting into a const buffer

Make pci_setup_device() write the bus ID directly into the allotted storage,
rather than using pci_name() as the address as that now returns a const
pointer.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>