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/stac9766.c

@@ -340,6 +340,7 @@ static int stac9766_codec_probe(struct snd_soc_codec *codec)
 
 	printk(KERN_INFO "STAC9766 SoC Audio Codec %s\n", STAC9766_VERSION);
 
+	codec->control_data = codec;	/* we don't use regmap! */
 	ret = snd_soc_new_ac97_codec(codec, &soc_ac97_ops, 0);
 	if (ret < 0)
 		goto codec_err;