ASoC: Drop exporting sn95031_get_mic_bias

sn95031_get_mic_bias() is not used outside this driver
and it is a static function now.
Thus drop exporting sn95031_get_mic_bias.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/codecs/sn95031.c

@@ -161,7 +161,6 @@ static unsigned int sn95031_get_mic_bias(struct snd_soc_codec *codec)
 	pr_debug("mic bias = %dmV\n", mic_bias);
 	return mic_bias;
 }
-EXPORT_SYMBOL_GPL(sn95031_get_mic_bias);
 /*end - adc helper functions */
 
 static inline unsigned int sn95031_read(struct snd_soc_codec *codec,