ARM: dts: r8a7790: sort subnodes of root node

Sort subnodes of root node to aid maintenance.

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>