R-Car sound driver is supporting Mem <-> SRU <-> SSI
transfer via DMAEngine.
The sound will be less noise if it uses SRU path
since it has FIFO.
This patch supports it.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>