* System sleep stats

Resource Power manager maintains information about system sleep and the time
each master spent in respective sleep modes. These were previously exported
through two modules, one for system and another for the respective master
votes. The two modules are now combined into a system stats drivers to provide
better visibility into system sleep modes.

Main node properties

- compatible
	Usage: Required
	Value type: <string>
	Definition: must be "qcom,system-stats".

- qcom,rpm-msg-ram
	Usage: Required
	Value type: <phandle>
	Definition: phandle to RPM's message ram registers.

- qcom,rpm-code-ram
	Usage: Required
	Value type: <phandle>
	Definition: phandle to RPM's code ram registers.

- qcom,masters:
	Usage: Required
	Value type: <string list>

Definition of memory DT phandles that system stats module is dependent on.

qcom,rpm-msg-ram:

The required phandle pointed to by qcom,rpm-msg-ram are:
Node properties:
- compatible:
	Usage: Required
	Value Type: <string>
	Definition: must be "qcom,rpm-msg-ram"

- reg:
	Usage: Required
	Value Type: <prop-encoded-array>
	Definition: Addresses and sizes for RPM address as visible to Apps and
	Stats address location.

- reg-names:
	Usage: Required
	Value Type: <stringlist>
	Definition: Address names. Must be "phys_addr_base" or "msg-ram-base".
			Must be specified in the same order as the
			corresponding addresses in the reg property.

qcom,rpm-code-ram:
The required phandle pointed to by qcom,rpm-msg-ram are:

Node properties:
- compatible:
	Usage: Required
	Value Type: <string>
	Definition: must be "qcom,rpm-code-ram".
- reg:
	Usage: Required
	Value Type: <prop-encoded-array>
	Definition: Address and size for RPM code address.

- reg-names:
	Usage: Required
	Value Type: <stringlist>
	Definition: Address names. Must be "msg-ram-base"

Example:

	rpm_code_ram: rpm-memory@0x68000 {
		compatible = "qcom,rpm-code-ram";
		reg = <0x68000 0x5000>;
		reg-name = "msg-ram-base";
	};

	rpm_msg_ram: memory@0x200000 {
		compatible = "qcom,rpm-msg-ram";
		reg = <0x200000 0x1000>,
			<0x290000 0x1000>;
		reg-names = "phys_addr_base",
			"code-ram-base";
	};

	qcom,system-stats@68140 {
		compatible = "qcom,system-stats";
		qcom,rpm-msg-ram = <&rpm_msg_ram>;
		qcom,rpm-code-ram = <&rpm_code_ram>;
		qcom,masters = "APSS", "MPSS", "ADSP", "SLPI";
	};