ASoC: rsnd: add Gen2 SRC and DMAEngine support

Renesas sound Gen2 has SRC (= Sampling Rate Converter)
which needs 2 DMAC.
The data path image when you use SRC on Gen2 is

[mem] -> Audio-DMAC -> SRC -> Audio-DMAC-peri-peri -> SSIU -> SSI

This patch support SRC and DMAEnine.
It is tested on R-Car H2 Lager board

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

include/sound/rcar_snd.h

@@ -56,9 +56,15 @@ struct rsnd_ssi_platform_info {
  */
 #define RSND_SCU_USE_HPBIF		(1 << 31) /* it needs RSND_SSI_DEPENDENT */
 
+#define RSND_SCU_SET(rate, _dma_id)		\
+	{ .flags = RSND_SCU_USE_HPBIF, .convert_rate = rate, .dma_id = _dma_id, }
+#define RSND_SCU_UNUSED				\
+	{ .flags = 0, .convert_rate = 0, .dma_id = 0, }
+
 struct rsnd_scu_platform_info {
 	u32 flags;
 	u32 convert_rate; /* sampling rate convert */
+	int dma_id; /* for Gen2 SCU */
 };
 
 /*