ASoC: Add snd_soc_kcontrol_codec() helper function

For CODEC controls snd_kcontrol_chip() currently returns a pointer to the
CODEC that registered the control. With the upcoming consolidation of
platform and CODEC controls this will change. Prepare for this by introducing
the snd_soc_kcontrol_codec() helper function that will hide the implementation
details of how the CODEC for a control can be obtained. This will allow us to
change this easily in the future.

The patch also updates all CODEC drivers to use the new helper function.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

sound/soc/codecs/ak4641.c

@@ -74,7 +74,7 @@ static int ak4641_set_deemph(struct snd_soc_codec *codec)
 static int ak4641_put_deemph(struct snd_kcontrol *kcontrol,
 				struct snd_ctl_elem_value *ucontrol)
 {
-	struct snd_soc_codec *codec = snd_kcontrol_chip(kcontrol);
+	struct snd_soc_codec *codec = snd_soc_kcontrol_codec(kcontrol);
 	struct ak4641_priv *ak4641 = snd_soc_codec_get_drvdata(codec);
 	int deemph = ucontrol->value.enumerated.item[0];
 
@@ -89,7 +89,7 @@ static int ak4641_put_deemph(struct snd_kcontrol *kcontrol,
 static int ak4641_get_deemph(struct snd_kcontrol *kcontrol,
 				struct snd_ctl_elem_value *ucontrol)
 {
-	struct snd_soc_codec *codec = snd_kcontrol_chip(kcontrol);
+	struct snd_soc_codec *codec = snd_soc_kcontrol_codec(kcontrol);
 	struct ak4641_priv *ak4641 = snd_soc_codec_get_drvdata(codec);
 
 	ucontrol->value.enumerated.item[0] = ak4641->deemph;