ARM: shmobile: bockw: use SSI DMAEngine for sound

R-Car sound driver is supporting Mem <-> SSI
direct transfer via DMAEngine.
Current HPB-DMA is using double plane transfer,
but the sound may have noise since SSI doesn't have 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>