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