spi: renesas,sh-msiof: Add r8a77961 support

Document R-Car M3-W+ (R8A77961) SoC bindings.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20201005112549.22222-1-geert+renesas@glider.beSigned-off-by: Mark Brown <broonie@kernel.org>

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

@@ -41,6 +41,7 @@ properties:
               - renesas,msiof-r8a774e1      # RZ/G2H
               - renesas,msiof-r8a7795       # R-Car H3
               - renesas,msiof-r8a7796       # R-Car M3-W
+              - renesas,msiof-r8a77961      # R-Car M3-W+
               - renesas,msiof-r8a77965      # R-Car M3-N
               - renesas,msiof-r8a77970      # R-Car V3M
               - renesas,msiof-r8a77980      # R-Car V3H