ASoC: omap-mcbsp: Support SND_SOC_DAIFMT_CBM_CFS for omap3/4

Add SND_SOC_DAIFMT_CBM_CFS support for omap3/omap4. The patch was tested on
a pandaboard-es board connected to the pcm1792a codec. mcbspx_fsx must
configured as output and mcbspx_clkx must be configured as input.

Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@linaro.org>