arm64: dts: Add Cavium ThunderX specific PMU

BugLink: http://bugs.launchpad.net/bugs/1559349

Add a compatible string for the Cavium ThunderX PMU.
Signed-off-by: Jan Glauber <jglauber@cavium.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
(cherry picked from linux-next commit 94085fe5)
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

Documentation/devicetree/bindings/arm/pmu.txt

@@ -24,6 +24,7 @@ Required properties:
 	"qcom,scorpion-pmu"
 	"qcom,scorpion-mp-pmu"
 	"qcom,krait-pmu"
+	"cavium,thunder-pmu"
 - interrupts : 1 combined interrupt or 1 per core. If the interrupt is a per-cpu
                interrupt (PPI) then 1 interrupt should be specified.
 

arch/arm64/boot/dts/cavium/thunder-88xx.dtsi

@@ -360,6 +360,11 @@ timer {
 		             <1 10 0xff01>;
 	};
 
+	pmu {
+		compatible = "cavium,thunder-pmu", "arm,armv8-pmuv3";
+		interrupts = <1 7 4>;
+	};
+
 	soc {
 		compatible = "simple-bus";
 		#address-cells = <2>;