pci: assign devfn to pci_dev before calling pci_device_iommu_address_space()

In function do_pci_register_device() in file hw/pci/pci.c, move the assignment
of pci_dev->devfn to the position before the call to
pci_device_iommu_address_space(pci_dev) which will use the value of
pci_dev->devfn.

Fixes: 9eda7d373e9c691c070eddcbe3467b991f67f6bd
    pci: Introduce helper to retrieve a PCI device's DMA address space

Cc: qemu-stable@nongnu.org
Signed-off-by: Le Tan <tamlokveer@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit efc8188e9398e54567b238b756eec2cc746cd2a4)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

hw/pci/pci.c

@@ -830,6 +830,7 @@ static PCIDevice *do_pci_register_device(PCIDevice *pci_dev, PCIBus *bus,
     }
 
     pci_dev->bus = bus;
+    pci_dev->devfn = devfn;
     dma_as = pci_device_iommu_address_space(pci_dev);
 
     memory_region_init_alias(&pci_dev->bus_master_enable_region,
@@ -839,7 +840,6 @@ static PCIDevice *do_pci_register_device(PCIDevice *pci_dev, PCIBus *bus,
     address_space_init(&pci_dev->bus_master_as, &pci_dev->bus_master_enable_region,
                        name);
 
-    pci_dev->devfn = devfn;
     pstrcpy(pci_dev->name, sizeof(pci_dev->name), name);
     pci_dev->irq_state = 0;
     pci_config_alloc(pci_dev);