ARM: dts: iwg20d-q7-common: Sound DMA support via BUSIF on DTS

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>