Bootcount Configuration
This is the implementation of the feature as described in
https://www.denx.de/wiki/DULG/UBootBootCountLimit.

Required Properties:
- compatible: must be "u-boot,bootcount-syscon".
- syscon: reference to the syscon device used.
- reg: contains address and size of the register and the location and size of the bootcount value.
	   The driver supports a 4 bytes register length and 2 and 4 bytes bootcount value length.
- reg-names: must be "syscon_reg", "offset";

Example:
	...
	syscon0: syscon@0 {
		compatible = "sandbox,syscon0";
		reg = <0x10 16>;
	};
	...
	bootcount@0 {
		compatible = "u-boot,bootcount-syscon";
		syscon = <&syscon0>;
		reg = <0x0 0x04>, <0x0 0x04>;
		reg-names = "syscon_reg", "offset";
	};