ASoC: Remove unused variable 'wm9090' in wm9090_probe

Eliminate below build warning:
  CC      sound/soc/codecs/wm9090.o
sound/soc/codecs/wm9090.c: In function 'wm9090_probe':
sound/soc/codecs/wm9090.c:550: warning: unused variable 'wm9090'
Signed-off-by: NAxel Lin <axel.lin@gmail.com>
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/codecs/wm9090.c

@@ -548,7 +548,6 @@ static int wm9090_set_bias_level(struct snd_soc_codec *codec,
 
 static int wm9090_probe(struct snd_soc_codec *codec)
 {
-	struct wm9090_priv *wm9090 = snd_soc_codec_get_drvdata(codec);
 	int ret;
 
 	ret = snd_soc_codec_set_cache_io(codec, 8, 16, SND_SOC_I2C);