dt-bindings: power: renesas,apmu: Document r8a7742 support

Document APMU and SMP enable method for RZ/G1H (also known as r8a7742)
SoC.
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Marian-Cristian Rotariu <marian-cristian.rotariu.rb@bp.renesas.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/power/renesas,apmu.yaml

@@ -18,6 +18,7 @@ properties:
   compatible:
     items:
       - enum:
+          - renesas,r8a7742-apmu  # RZ/G1H
           - renesas,r8a7743-apmu  # RZ/G1M
           - renesas,r8a7744-apmu  # RZ/G1N
           - renesas,r8a7745-apmu  # RZ/G1E