dt-bindings: clock: renesas: cpg-mssr: Document r8a7742 binding

Add binding documentation for the RZ/G1H (R8A7742) Clock Pulse Generator
driver.
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/1587678050-23468-7-git-send-email-prabhakar.mahadev-lad.rj@bp.renesas.comSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Documentation/devicetree/bindings/clock/renesas,cpg-mssr.yaml

@@ -25,6 +25,7 @@ properties:
   compatible:
     enum:
       - renesas,r7s9210-cpg-mssr  # RZ/A2
+      - renesas,r8a7742-cpg-mssr  # RZ/G1H
       - renesas,r8a7743-cpg-mssr  # RZ/G1M
       - renesas,r8a7744-cpg-mssr  # RZ/G1N
       - renesas,r8a7745-cpg-mssr  # RZ/G1E