ASoC: davinci: Add edma dmaengine platform driver

Platform driver glue for SoC using eDMA3 to use dmaengine PCM.
The maximum number of periods need to be limited to 19 since the
edma dmaengine driver limits the paRAM slot use for audio at
in cyclic mode.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>