arm64: dts: h3ulcb: add H3ULCB board DT bindings

Add H3ULCB Device tree bindings Documentation, listing it as a supported
board.

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