ASoC: atmel-pcm: dma support based on pcm dmaengine

Specify overrun bit in interrupt mask
Add dmaengine specific routines

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
[voice.shen@atmel.com: adapt to soc dmaengine framework]
Signed-off-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>