[media] em28xx-audio: disconnect before freeing URBs

URBs might be in usage. Disconnect the device before freeing
them.
Reviewed-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Tested-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/usb/em28xx/em28xx-audio.c

@@ -956,6 +956,7 @@ static int em28xx_audio_fini(struct em28xx *dev)
 		return 0;
 	}
 
+	snd_card_disconnect(dev->adev.sndcard);
 	em28xx_audio_free_urb(dev);
 
 	if (dev->adev.sndcard) {