ARM: dts: r8a7794: Add SMP support

Add the device tree node for the Advanced Power Management Unit (APMU).
Use the "enable-method" prop to  point out that the APMU should be used
for the SMP support.
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7794.dtsi

@@ -37,6 +37,7 @@ aliases {
 	cpus {
 		#address-cells = <1>;
 		#size-cells = <0>;
+		enable-method = "renesas,apmu";
 
 		cpu0: cpu@0 {
 			device_type = "cpu";
@@ -66,6 +67,12 @@ L2_CA7: cache-controller-0 {
 		};
 	};
 
+	apmu@e6151000 {
+		compatible = "renesas,r8a7794-apmu", "renesas,apmu";
+		reg = <0 0xe6151000 0 0x188>;
+		cpus = <&cpu0 &cpu1>;
+	};
+
 	gic: interrupt-controller@f1001000 {
 		compatible = "arm,gic-400";
 		#interrupt-cells = <3>;