dt-bindings: thermal: rcar-gen3-thermal: Add r8a774a1 support

Document RZ/G2M (R8A774A1) SoC bindings.

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

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

@@ -7,6 +7,7 @@ inside the LSI.
 Required properties:
 - compatible		: "renesas,<soctype>-thermal",
 			  Examples with soctypes are:
+			    - "renesas,r8a774a1-thermal" (RZ/G2M)
 			    - "renesas,r8a7795-thermal" (R-Car H3)
 			    - "renesas,r8a7796-thermal" (R-Car M3-W)
 			    - "renesas,r8a77965-thermal" (R-Car M3-N)