dt-bindings: nvmem: Add Spreadtrum eFuse controller documentation

= Spreadtrum eFuse device tree bindings =

Required properties:

- compatible: Should be "sprd,ums312-efuse".

- reg: Specify the address offset of efuse controller.

- clock-names: Should be "enable".

- clocks: The phandle and specifier referencing the controller's clock.

- hwlocks: Reference to a phandle of a hwlock provider node.

= Data cells =

Are child nodes of eFuse, bindings of which as described in

bindings/nvmem/nvmem.txt

Example:

	ap_efuse: efuse@32240000 {

		compatible = "sprd,ums312-efuse";

		reg = <0 0x32240000 0 0x10000>;

		clock-names = "enable";

		hwlocks = <&hwlock 8>;

		clocks = <&aonapb_gate CLK_EFUSE_EB>;

		/* Data cells */

		thermal_calib: calib@10 {

			reg = <0x10 0x2>;

		};

	};

= Data consumers =

Are device nodes which consume nvmem data cells.

Example:

	thermal {

		...

		nvmem-cells = <&thermal_calib>;

		nvmem-cell-names = "calibration";

	};