ARM: dts: bcm2837: Enable PMU on Raspberry Pi 3

This enables the PMU (performance monitoring unit) on Raspberry Pi 3.
In order to make it work on ARM and ARM64, we need to specify two
compatible strings.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>

arch/arm/boot/dts/bcm2837.dtsi

@@ -17,6 +17,12 @@
 		};
 	};
 
+	arm-pmu {
+		compatible = "arm,cortex-a53-pmu", "arm,cortex-a7-pmu";
+		interrupt-parent = <&local_intc>;
+		interrupts = <9 IRQ_TYPE_LEVEL_HIGH>;
+	};
+
 	timer {
 		compatible = "arm,armv7-timer";
 		interrupt-parent = <&local_intc>;