FS polarity can be either rising or falling edge in McASP. Instead of
accessing the registers in every switch/case set a flag and write the
registers after the switch for the invert configuration.
This change will help when adding support for more formats also.
Signed-off-by: NPeter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: NMark Brown <broonie@linaro.org>