arm64: dts: renesas: initial V3MSK board device tree

Add the initial device  tree for the V3M Starter Kit board.
The board has 1 debug serial port (SCIF0); include support for it,
so that the serial console can work.

Based on the original (and large) patch by Vladimir Barinov.

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