dt-bindings: thermal: rcar-gen3-thermal: Add r8a77961 support

Document R-Car M3-W+ (R8A77961) SoC bindings.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200306105503.24267-2-geert+renesas@glider.be

Documentation/devicetree/bindings/thermal/rcar-gen3-thermal.txt

@@ -11,6 +11,7 @@ Required properties:
 			    - "renesas,r8a774b1-thermal" (RZ/G2N)
 			    - "renesas,r8a7795-thermal" (R-Car H3)
 			    - "renesas,r8a7796-thermal" (R-Car M3-W)
+			    - "renesas,r8a77961-thermal" (R-Car M3-W+)
 			    - "renesas,r8a77965-thermal" (R-Car M3-N)
 			    - "renesas,r8a77980-thermal" (R-Car V3H)
 - reg			: Address ranges of the thermal registers. Each sensor