arm64: dts: r8a7795: Use SYSC "always-on" PM Domain for RWDT node

Hook up the RWDT device node to the SYSC "always-on" PM Domain, for a
more consistent device-power-area description in DT.

Cfr. commit 38dbb45e ("arm64: dts: r8a7795: Use SYSC "always-on" PM
Domain")

Fixes: f43838a7ae014cba ("arm64: dts: r8a7795: Add RWDT node")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/r8a7795.dtsi

@@ -168,7 +168,7 @@ wdt0: watchdog@e6020000 {
 			compatible = "renesas,r8a7795-wdt", "renesas,rcar-gen3-wdt";
 			reg = <0 0xe6020000 0 0x0c>;
 			clocks = <&cpg CPG_MOD 402>;
-			power-domains = <&cpg>;
+			power-domains = <&sysc R8A7795_PD_ALWAYS_ON>;
 			status = "disabled";
 		};