ASoC: rsnd: add common DMAEngine method

R-Car Sound driver will support DMA transfer in the future,
then, SSI/SRU/SRC will use it.
Current R-Car can't use soc-dmaengine-pcm.c since its DMAEngine
doesn't support dmaengine_prep_dma_cyclic(),
and SSI needs double plane transfer (which needs special submit) on DMAC.
This patch adds common DMAEngine method for it

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@linaro.org>