ASoC: Don't use control_data to get struct wm8994

This will support refactoring to make use of the regmap API more directly
in the core.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/sound/soc/codecs/wm8994.h b/sound/soc/codecs/wm8994.h
index 1087425..c3e71d7 100644
--- a/sound/soc/codecs/wm8994.h
+++ b/sound/soc/codecs/wm8994.h
@@ -70,10 +70,11 @@
 #define WM8994_NUM_DRC 3
 #define WM8994_NUM_EQ  3
 
+struct wm8994;
+
 struct wm8994_priv {
 	struct wm_hubs_data hubs;
-	enum snd_soc_control_type control_type;
-	void *control_data;
+	struct wm8994 *wm8994;
 	struct snd_soc_codec *codec;
 	int sysclk[2];
 	int sysclk_rate[2];