ARM: mvebu: Enable Performance Monitor Unit on Armada 380/385 SoC

The Armada 380 and 385 SoCs have a Cortex-A9 CPU, so the PMU is available
to be used. This commit enables it in the devicetree.
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>

arch/arm/boot/dts/armada-38x.dtsi

@@ -63,6 +63,11 @@ aliases {
 		serial1 = &uart1;
 	};
 
+	pmu {
+		compatible = "arm,cortex-a9-pmu";
+		interrupts-extended = <&mpic 3>;
+	};
+
 	soc {
 		compatible = "marvell,armada380-mbus", "simple-bus";
 		#address-cells = <2>;