ASoC: Remove unused control type from wm8978 driver

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/codecs/wm8978.c

@@ -50,7 +50,6 @@ static const u16 wm8978_reg[WM8978_CACHEREGNUM] = {
 
 /* codec private data */
 struct wm8978_priv {
-	enum snd_soc_control_type control_type;
 	unsigned int f_pllout;
 	unsigned int f_mclk;
 	unsigned int f_256fs;