spi: renesas,sh-msiof: Add r8a779a0 support

Document R-Car V3U (R8A779A0) SoC bindings.
Signed-off-by: NWolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20210108103522.2025880-1-geert+renesas@glider.beSigned-off-by: NMark Brown <broonie@kernel.org>

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

@@ -47,6 +47,7 @@ properties:
               - renesas,msiof-r8a77980      # R-Car V3H
               - renesas,msiof-r8a77990      # R-Car E3
               - renesas,msiof-r8a77995      # R-Car D3
+              - renesas,msiof-r8a779a0      # R-Car V3U
           - const: renesas,rcar-gen3-msiof  # generic R-Car Gen3 and RZ/G2
                                             # compatible device
       - items: