ARM: dts: r8a7794: sort subnodes of root node

Sort the subnodes of the soc node to improve maintainability.
The sort key is the address on the bus with instances of the same
IP block grouped together.

Also re-align comment of audio_clka to match other R-Car SoCs.

This patch should not introduce any functional change.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>