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: NAlexey Kardashevskiy <aik@ozlabs.ru>
Acked-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NAlexander Graf <agraf@suse.de>

hw/ppc/spapr_pci.c

@@ -65,22 +65,14 @@ static PCIDevice *find_dev(sPAPREnvironment *spapr, uint64_t buid,
 {
     sPAPRPHBState *sphb = find_phb(spapr, buid);
     PCIHostState *phb = PCI_HOST_BRIDGE(sphb);
-    BusState *bus = BUS(phb->bus);
-    BusChild *kid;
+    int bus_num = (config_addr >> 16) & 0xFF;
     int devfn = (config_addr >> 8) & 0xFF;
 
     if (!phb) {
         return NULL;
     }
 
-    QTAILQ_FOREACH(kid, &bus->children, sibling) {
-        PCIDevice *dev = (PCIDevice *)kid->child;
-        if (dev->devfn == devfn) {
-            return dev;
-        }
-    }
-
-    return NULL;
+    return pci_find_device(phb->bus, bus_num, devfn);
 }
 
 static uint32_t rtas_pci_cfgaddr(uint32_t arg)