pci: memory leak of PCIDevice::rom_file

PCIDevice::rom_file is leaked.
PCIDevice::rom_file is allocated in pci_qdev_init(), but not freed anywhere.
free it in qemu_unregister_device().
Signed-off-by: NIsaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

hw/pci.c

@@ -833,6 +833,7 @@ static int pci_unregister_device(DeviceState *dev)
 
     pci_unregister_io_regions(pci_dev);
     pci_del_option_rom(pci_dev);
+    qemu_free(pci_dev->romfile);
     do_pci_unregister_device(pci_dev);
     return 0;
 }