ASoC: AC97 doesn't use regmap by default

Since commit 38cbf9598f
("ASoC: core: Try to use regmap if the driver doesn't set up any I/O")
any ASoC codec which doesn't set codec::control_data is assumed
to use regmap.  That doesn't work with AC97 so this workaround
sets the codec::control_data member to a random value to restore
proper behaviour.

Tested with WM9712.

Signed-off-by: Manuel Lauss <manuel.lauss@googlemail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/codecs/wm9713.c

@@ -1196,6 +1196,7 @@ static int wm9713_soc_probe(struct snd_soc_codec *codec)
 	if (wm9713 == NULL)
 		return -ENOMEM;
 	snd_soc_codec_set_drvdata(codec, wm9713);
+	codec->control_data = wm9713;	/* we don't use regmap! */
 
 	ret = snd_soc_new_ac97_codec(codec, &soc_ac97_ops, 0);
 	if (ret < 0)