[media] media: au0828 fix to clear enable/disable/change source handlers

Fix to clear enable/disable/change source handlers in the media device
when media device is unregistered in au0828_unregister_media_device().
When au0828 module is removed, snd-usb-audio shouldn't call the handlers.
Clearing will ensure snd-usb-audio won't call them once au0828 is removed.

[mchehab@osg.samsung.com: fix a compilation breakage]
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/usb/au0828/au0828-core.c

@@ -137,6 +137,11 @@ static void au0828_unregister_media_device(struct au0828_dev *dev)
 #ifdef CONFIG_MEDIA_CONTROLLER
 	if (dev->media_dev &&
 		media_devnode_is_registered(&dev->media_dev->devnode)) {
+		/* clear enable_source, disable_source */
+		dev->media_dev->source_priv = NULL;
+		dev->media_dev->enable_source = NULL;
+		dev->media_dev->disable_source = NULL;
+
 		media_device_unregister(dev->media_dev);
 		media_device_cleanup(dev->media_dev);
 		dev->media_dev = NULL;