ASoC: mmp: add audio dma support

mmp-pcm handle audio dma based on soc-dmaengine
Support mmp and pxa910

Signed-off-by: Zhangfei Gao <zhangfei.gao@marvell.com>
Signed-off-by: Leo Yan <leoy@marvell.com>
Signed-off-by: Qiao Zhou <zhouqiao@marvell.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>