DMA transfer to/from SSIU

     DMA
[MEM] -> [SSIU] -> [SSI]

     DMA
[MEM] <- [SSIU] <- [SSI]
Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>