MSM M4M hardware monitor device

m4m-hwmon is a device that represents the MSM M4M hardware monitors
that can be used to measure the various types of requests in the MSM M4M.

Required properties:
- compatible:		Must be "qcom,m4m-hwmon"
- reg:			Pairs of physical base addresses and region sizes of
			memory mapped registers.
- interrupts:		Lists the threshold IRQ.
- qcom,counter-event-sel: Array of counter and event selection values.
- qcom,target-dev:	The DT device that is monitored by this MSM M4M
			counter configuration.

Example:
	qcom,m4m-hwmon {
		compatible = "qcom,m4m-hwmon";
		reg = <0x6530000 0x160>;
		interrupts = <0 19 4>;
		qcom,counter-event-sel = <4 0x100>;
		qcom,target-dev = <&m4m_cache>;
	};