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

Documentation/devicetree/bindings/arm/renesas.yaml

@@ -118,6 +118,14 @@ properties:
 
       - description: RZ/G2N (R8A774B1)
         items:
+          - enum:
+              - hoperun,hihope-rzg2n # HopeRun HiHope RZ/G2N platform
+          - const: renesas,r8a774b1
+
+      - items:
+          - enum:
+              - hoperun,hihope-rzg2-ex # HopeRun expansion board for HiHope RZ/G2 platforms
+          - const: hoperun,hihope-rzg2n
           - const: renesas,r8a774b1
 
       - description: RZ/G2E (R8A774C0)