dt-bindings: power: rcar-sysc: Document r8a7742 SYSC binding

Add binding documentation for the RZ/G1H (R8A7742) SYSC block.
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Marian-Cristian Rotariu <marian-cristian.rotariu.rb@bp.renesas.com>
Link: https://lore.kernel.org/r/1587678050-23468-2-git-send-email-prabhakar.mahadev-lad.rj@bp.renesas.comSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Documentation/devicetree/bindings/power/renesas,rcar-sysc.yaml

@@ -17,6 +17,7 @@ description:
 properties:
   compatible:
     enum:
+      - renesas,r8a7742-sysc  # RZ/G1H
       - renesas,r8a7743-sysc  # RZ/G1M
       - renesas,r8a7744-sysc  # RZ/G1N
       - renesas,r8a7745-sysc  # RZ/G1E