L2 cache performance monitor unit

L2 cache controllers have a performance monitor unit to measure
events such as cache hits and misses. There is one L2 cache PMU
for each cluster of CPUs.

Required properties:

- compatible : should be "qcom,qcom-l2cache-pmu"
- interrupts : 1 interrupt for each cluster.
- qcom,cpu-affinity: specifies the id of the first CPU in the cluster.

Example:

	l2cache-pmu {
		    compatible = "qcom,qcom-l2cache-pmu";
		    interrupts = <0 0 1>, <0 8 1>;
		    qcom,cpu-affinity = <0>, <2>
	};