ASoC: tlv320aic23: Clear TLV320AIC23_MS_MASTER bit for slave mode

According to the datasheet:

Digital Audio Interface Format (07h) register:
BIT6:	Master/slave mode
	0: Slave
	1: Master

Current code sets TLV320AIC23_MS_MASTER bit for master mode,
but does not clear it for slave mode.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/sound/soc/codecs/tlv320aic23.c b/sound/soc/codecs/tlv320aic23.c
index ab27dbc..336de8f 100644
--- a/sound/soc/codecs/tlv320aic23.c
+++ b/sound/soc/codecs/tlv320aic23.c
@@ -430,6 +430,7 @@
 		iface_reg |= TLV320AIC23_MS_MASTER;
 		break;
 	case SND_SOC_DAIFMT_CBS_CFS:
+		iface_reg &= ~TLV320AIC23_MS_MASTER;
 		break;
 	default:
 		return -EINVAL;