ARM: mvebu: Enable Performance Monitor Unit on Armada XP/370 SoCs

The Armada 370 and XP SoCs have Cortex-A9 compatible CPUs, and with a
Performance Monitoring Unit.

Enable it so that we can have hardware-assisted perf support.
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-370-xp.dtsi

@@ -73,6 +73,11 @@ cpu@0 {
 		};
 	};
 
+	pmu {
+		compatible = "arm,cortex-a9-pmu";
+		interrupts-extended = <&mpic 3>;
+	};
+
 	soc {
 		#address-cells = <2>;
 		#size-cells = <1>;