staging: unisys: fix up device_destroy

Visorbus_remove_instance calls device_unregister which in turn will call
visorbus_release_busdevice. The function visorbus_release_busdevice was
freeing the visor_device. The code in visorbus_remove_instance was then
trying to reference the visor_device. This patch cleans up the code so
the visor_device is not referenced after the unregister.
Signed-off-by: David Kershner <david.kershner@unisys.com>
Reviewed-by: Tim Sell <timothy.sell@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/unisys/visorbus/visorbus_main.c

@@ -181,6 +181,7 @@ static void visorbus_release_busdevice(struct device *xdev)
 
 	debugfs_remove(dev->debugfs_client_bus_info);
 	debugfs_remove_recursive(dev->debugfs_dir);
+	visorchannel_destroy(dev->visorchannel);
 	kfree(dev);
 }
 
@@ -1069,11 +1070,11 @@ void visorbus_remove_instance(struct visor_device *dev)
 	 * successfully been able to trace thru the code to see where/how
 	 * release() gets called.  But I know it does.
 	 */
-	visorchannel_destroy(dev->visorchannel);
 	kfree(dev->vbus_hdr_info);
 	list_del(&dev->list_all);
+	if (dev->pending_msg_hdr)
+		visorbus_response(dev, 0, CONTROLVM_BUS_DESTROY);
 	device_unregister(&dev->device);
-	visorbus_response(dev, 0, CONTROLVM_BUS_DESTROY);
 }
 
 /*