arm64: dts: renesas: r8a78000: Add PSCI node

Describe SMC based PSCI access in SoC DT.  The system can interact with
TFA BL31 PSCI provider running on the Cortex-A cores via SMC calls.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20260513225037.49803-1-marek.vasut+renesas@mailbox.org
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Author: Marek Vasut

arch/arm64/boot/dts/renesas/r8a78000.dtsi

@@ -665,6 +665,11 @@
 		/* clock-frequency must be set on board */
 	};
 
+	psci {
+		compatible = "arm,psci-1.0";
+		method = "smc";
+	};
+
 	/* External SCIF clock - to be overridden by boards that provide it */
 	scif_clk: scif-clk {
 		compatible = "fixed-clock";