ASoC: rsnd: recover PIO mode for new dma interface

Renesas sound driver needs 1st/2nd DMA interface,
and 1st DMA is using DMAEngine, and 2nd is using local method now.
2nd DMA had been DMAEngine, but it was moved to local method by previous
patchset. But then, it lost PIO mode fallback when probe.
this patch recovers it.

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