ASoC: Remove unused mutex from WM9090 driver

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

sound/soc/codecs/wm9090.c

@@ -139,7 +139,6 @@ static const u16 wm9090_reg_defaults[] = {
 
 /* This struct is used to save the context */
 struct wm9090_priv {
-	struct mutex mutex;
 	struct wm9090_platform_data pdata;
 	void *control_data;
 };
@@ -663,7 +662,6 @@ static int wm9090_i2c_probe(struct i2c_client *i2c,
 
 	i2c_set_clientdata(i2c, wm9090);
 	wm9090->control_data = i2c;
-	mutex_init(&wm9090->mutex);
 
 	ret =  snd_soc_register_codec(&i2c->dev,
 			&soc_codec_dev_wm9090,  NULL, 0);