arm64: dts: renesas: r8a77990: Add Audio-DMAC and Sound device nodes

This patch adds Audio-DMAC0 device node and Sound device node
for the R8A77990 SoC.

Based on work by Takeshi Kihara and Hai Nguyen Pham.

Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com>
[simon: dropped include update, which is already present]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>