spapr-pci: fix config space access to support bridges

spapr-pci: fix config space access to support bridges

spapr-pci config space accessors use find_dev() to find a PCI device.
However find_dev() only searched on a primary bus and did not do
recursive search through secondary buses so config space access was not
possible for devices other that on a primary bus.

This fixed find_dev() by using the PCI API pci_find_device() function.
This effectively enabled pci bridges on spapr.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Alexander Graf <agraf@suse.de>