arm64: dts: marvell: armada-ap806: reserve PSCI area

The memory area [0x4000000-0x4200000[ is occupied by the PSCI firmware. Any
attempt to access it from Linux leads to an immediate crash.

So let's make the same memory reservation as the vendor kernel.

[gregory: added as comment that this region matches the mainline U-boot]
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>

arch/arm64/boot/dts/marvell/armada-ap806.dtsi

@@ -28,6 +28,23 @@ psci {
 		method = "smc";
 	};
 
+	reserved-memory {
+		#address-cells = <2>;
+		#size-cells = <2>;
+		ranges;
+
+		/*
+		 * This area matches the mapping done with a
+		 * mainline U-Boot, and should be updated by the
+		 * bootloader.
+		 */
+
+		psci-area@4000000 {
+			reg = <0x0 0x4000000 0x0 0x200000>;
+			no-map;
+		};
+	};
+
 	ap806 {
 		#address-cells = <2>;
 		#size-cells = <2>;