dt-bindings: arm: renesas: Add HopeRun RZ/G2N boards

This patch adds board HiHope RZ/G2N (the main board, powered by
the R8A774B1) and board HiHope RZ/G2 EX (the expansion board
that sits on top of the HiHope RZ/G2N). Both boards are made
by Jiangsu HopeRun Software Co., Ltd. (a.k.a. HopeRun).

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1568724492-32087-1-git-send-email-biju.das@bp.renesas.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>