ASoC: rk3308_codec: add some delay to wait micbias is stable

To avoid bring some noise dues to unstable micbias.

Change-Id: I0127505f0adeacda5d852ae3cefae2fb5f4ee9d2
Signed-off-by: Xing Zheng <zhengxing@rock-chips.com>

sound/soc/codecs/rk3308_codec.c

@@ -2879,6 +2879,9 @@ static int rk3308_codec_micbias_enable(struct rk3308_codec_priv *rk3308,
 				   RK3308_ADC_MIC_BIAS_BUF_EN,
 				   RK3308_ADC_MIC_BIAS_BUF_EN);
 
+	/* waiting micbias stabled*/
+	mdelay(50);
+
 	rk3308->enable_micbias = true;
 
 	return 0;