arm64: dts: renesas: r8a77961: Add RWDT node

Add a device node for the RCLK Watchdog Timer (RWDT) on the Renesas
R-Car M3-W+ (r8a77961) SoC.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Tested-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Link: https://lore.kernel.org/r/20191216124740.16647-2-geert+renesas@glider.be

arch/arm64/boot/dts/renesas/r8a77961.dtsi

@@ -319,8 +319,13 @@ soc {
 		ranges;
 
 		rwdt: watchdog@e6020000 {
+			compatible = "renesas,r8a77961-wdt",
+				     "renesas,rcar-gen3-wdt";
 			reg = <0 0xe6020000 0 0x0c>;
-			/* placeholder */
+			clocks = <&cpg CPG_MOD 402>;
+			power-domains = <&sysc R8A77961_PD_ALWAYS_ON>;
+			resets = <&cpg 402>;
+			status = "disabled";
 		};
 
 		gpio2: gpio@e6052000 {