ARM: dts: atlas6: add cortex-a9-pmu compatible PMU node

add cortex-a9-pmu node to make the performance monitor unit work on atlas6.

Signed-off-by: Ye He <Ye.He@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>

arch/arm/boot/dts/atlas6.dtsi

@@ -39,6 +39,11 @@
 		};
 	};
 
+	arm-pmu {
+		compatible = "arm,cortex-a9-pmu";
+		interrupts = <29>;
+	};
+
 	axi {
 		compatible = "simple-bus";
 		#address-cells = <1>;