hw/pci-host: Allow extended config space access for Designware PCIe host

In pcie_bus_realize(), a root bus is realized as a PCIe bus and a non-root
bus is realized as a PCIe bus if its parent bus is a PCIe bus. However,
the child bus "dw-pcie" is realized before the parent bus "pcie" which is
the root PCIe bus. Thus, the extended configuration space is not accessible
on "dw-pcie". The issue can be resolved by adding the
PCI_BUS_EXTENDED_CONFIG_SPACE flag to "pcie" before "dw-pcie" is realized.

Signed-off-by: Jason Chien <jason.chien@sifive.com>
Message-Id: <20230809102257.25121-1-jason.chien@sifive.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Frank Chang <frank.chang@sifive.com>
Signed-off-by: Jason Chien &lt;<a href="mailto:jason.chien@sifive.com" target="_blank">jason.chien@sifive.com</a>&gt;<br>

hw/pci-host/designware.c

@@ -694,6 +694,7 @@ static void designware_pcie_host_realize(DeviceState *dev, Error **errp)
                                      &s->pci.io,
                                      0, 4,
                                      TYPE_PCIE_BUS);
+    pci->bus->flags |= PCI_BUS_EXTENDED_CONFIG_SPACE;
 
     memory_region_init(&s->pci.address_space_root,
                        OBJECT(s),