bindings: Add device-tree bindings for hwkm driver

HWKM (Hardware Key Manager)

The HWKM driver is a platform device driver that helps

communicating with both the master and slave blocks of the

hardware key manager to issue commands to perform key operations

mainly required for storage encryption.

Required properties:

- compatible : Should be "qcom,hwkm".

- reg: Register set for both master and slaves.

- reg-names : Identifiers for parsing master and slave regs.

- clocks : clocks needed for operating master and the slave.

- clock-names : name identifiers corresponding to the clocks.

- qcom,enable-hwkm-clk: to ensure clocks can be handled by HLOS.

- qcom,op-freq-hz: Max frequency of the listed clocks.

Example:

	qcom_hwkm: hwkm@10c0000 {

		compatible = "qcom,hwkm";

		reg = <0x10c0000 0x9000>, <0x1d90000 0x9000>;

		reg-names = "km_master", "ice_slave";

		qcom,enable-hwkm-clk;

		clock-names = "km_clk_src";

		clocks = <&clock_rpmh RPMH_HWKM_CLK>;

		qcom,op-freq-hz = <75000000>;

	};