spi: renesas,sh-msiof: Add r8a7742 support

Document RZ/G1H (R8A7742) SoC bindings.
Signed-off-by: NLad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: NMarian-Cristian Rotariu <marian-cristian.rotariu.rb@bp.renesas.com>
Reviewed-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/1591736054-568-2-git-send-email-prabhakar.mahadev-lad.rj@bp.renesas.comSigned-off-by: NMark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/renesas,sh-msiof.yaml

@@ -21,6 +21,7 @@ properties:
                                             # device
       - items:
           - enum:
+              - renesas,msiof-r8a7742       # RZ/G1H
               - renesas,msiof-r8a7743       # RZ/G1M
               - renesas,msiof-r8a7744       # RZ/G1N
               - renesas,msiof-r8a7745       # RZ/G1E