hw/arm/virt: Allow zero address for PCI IO space

Currently PCI IO address 0 is not allowed even though
the IO space starts from 0. This update makes  PCI IO
address 0 usable.

CC: Peter Maydell <peter.maydell@linaro.org>
CC: Andrew Jones <drjones@redhat.com>
Signed-off-by: NAlexander Gordeev <agordeev@redhat.com>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/arm/virt.c

@@ -1162,6 +1162,7 @@ static void virt_class_init(ObjectClass *oc, void *data)
     mc->has_dynamic_sysbus = true;
     mc->block_default_type = IF_VIRTIO;
     mc->no_cdrom = 1;
+    mc->pci_allow_0_address = true;
 }
 
 static const TypeInfo machvirt_info = {