ARM: dts: r8a7742-iwg21d-q7: Sound DMA support via DVC on DTS

Enable sound with DMA support on carrier board.

DMA transfer uses DVC

     DMA               DMApp
[MEM] -> [SRC] -> [DVC] -> [SSIU] -> [SSI]

     DMA               DMApp
[MEM] <- [DVC] <- [SRC] <- [SSIU] <- [SSI]

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Marian-Cristian Rotariu <marian-cristian.rotariu.rb@bp.renesas.com>
Link: https://lore.kernel.org/r/1590611013-26029-4-git-send-email-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>