pci_bridge: fix typo in comment

Signed-off-by: Mao Zhongyi <maozhongyi@cmss.chinamobile.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/pci/pci_bridge.c

@@ -399,7 +399,7 @@ void pci_bridge_exitfn(PCIDevice *pci_dev)
 
 /*
  * before qdev initialization(qdev_init()), this function sets bus_name and
- * map_irq callback which are necessry for pci_bridge_initfn() to
+ * map_irq callback which are necessary for pci_bridge_initfn() to
  * initialize bus.
  */
 void pci_bridge_map_irq(PCIBridge *br, const char* bus_name,