dt-bindings: Introduce soc sleep stats bindings for QTI SoCs

* SoC Sleep Stats

Always On Processor/Resource Power Manager maintains statistics of the SoC

sleep modes involving lowering or powering down of the backbone rails - Cx

and Mx and the oscillator clock XO.

Statistics includes SoC sleep mode type, number of times low power mode were

entered, time of last entry, time of last exit and accumulated sleep duration.

SoC Sleep Stats driver provides sysfs interface to display this information.

Properties:

- compatible:

	Usage: required

	Value type: <string>

	Definition: Should be "qcom,rpmh-sleep-stats" or "qcom,rpm-sleep-stats".

- reg:

	Usage: required

	Value type: <prop-encoded-array>

	Definition: The base address on the Always On Processor or Resource Power

		    Manager from where the stats are read.

EXAMPLE 1:

	rpmh_sleep_stats: soc-sleep-stats@c3f0000 {

		compatible = "qcom,rpmh-sleep-stats";

		reg = <0 0xc3f0000 0 0x400>;

	};

EXAMPLE 2:

	rpm_sleep_stats: soc-sleep-stats@4690000 {

		compatible = "qcom,rpm-sleep-stats";

		reg = <0 0x04690000 0 0x400>;

	};