dt-bindings: arm: renesas: Document iW-RainboW-G21M-Qseven-RZG1H SoM

Document the iW-RainboW-G21M-Qseven-RZG1H device tree bindings,
listing it as a supported system on module.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Marian-Cristian Rotariu <marian-cristian.rotariu.rb@bp.renesas.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1588542414-14826-8-git-send-email-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Documentation/devicetree/bindings/arm/renesas.yaml

@@ -54,6 +54,9 @@ properties:
 
       - description: RZ/G1H (R8A77420)
         items:
+          - enum:
+              # iWave Systems RZ/G1H Qseven System On Module (iW-RainboW-G21M-Qseven)
+              - iwave,g21m
           - const: renesas,r8a7742
 
       - description: RZ/G1M (R8A77430)