ARM PMU based bandwidth monitor device

armbw-pm is a device that represents the use of the PMU present in ARM cores
to measure the bandwidth of bus access traffic from the cores.

Required properties:
- compatible:			Must be "qcom,armbw-pm"
- interrupts:			Lists the required interrupt settings
- qcom,bytes-per-beat:	The number of bytes present in each access

Example:
	qcom,armbw-pm {
		compatible = "qcom,armbw-pm";
		interrupts = <1 7 0xF1>;
		qcom,bytes-per-beat = <16>;
	};