Define the SILK board dependent part of the R8A7794 sound  device node.
Add device node for Asahi Kasei AK4643 stereo codec to the I2C1 bus.
Add the "simple-audio-card" device node to interconnect the SoC sound
device  and the codec.

This patch is based on the commit 493b4da7 ("ARM: dts: porter: add
sound support").
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>