arm64: dts: h3ulcb: initial device tree

Add the initial device tree for the R8A7795 SoC based H3ULCB low cost
board.

This commit supports the following peripherals:
- SCIF (console)

Signed-off-by: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>