ASoC: ep93xx: Setup dma data in DAI probe

This allows us to access the DAI DMA data when we create the PCM. We'll use
this when converting ep39xx to generic DMA engine PCM driver.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>