pci: pmon not update first bridge bus PCI_PRIBUS_1, which is a dummy device.

Change-Id: I5d62d461d612728423d06ccfd28c7558258463a7
Signed-off-by: QiaoChong <qiaochong@loongson.cn>

sys/dev/pci/pciconf.c

@@ -568,7 +568,8 @@ _pci_query_dev_func (struct pci_device *dev, pcitag_t tag, int initialise)
             tmp = _pci_conf_read(pcidev->pa.pa_tag, PCI_PRIBUS_1);
             tmp &= 0xff00ffff;
             tmp |= pd->bridge.secbus_num << 16;
-            _pci_conf_write(pcidev->pa.pa_tag, PCI_PRIBUS_1, tmp);
+	    if(pcidev->parent)
+		    _pci_conf_write(pcidev->pa.pa_tag, PCI_PRIBUS_1, tmp);
         }
 
         pd->bridge.secbus = pmalloc(sizeof(struct pci_bus));