* Xtal Clock bindings for Marvell Armada 37xx SoCs

Marvell Armada 37xx SoCs allow to determine the xtal clock frequencies by
reading the gpio latch register.

This node must be a subnode of the node exposing the register address
of the GPIO block where the gpio latch is located.

Required properties:
- compatible : shall be one of the following:
	"marvell,armada-3700-xtal-clock"
- #clock-cells : from common clock binding; shall be set to 0

Optional properties:
- clock-output-names : from common clock binding; allows overwrite default clock
	output names ("xtal")

Example:
gpio1: gpio@13800 {
	compatible = "marvell,armada-3700-gpio", "syscon", "simple-mfd";
	reg = <0x13800 0x1000>;

	xtalclk: xtal-clk {
		compatible = "marvell,armada-3700-xtal-clock";
		clock-output-names = "xtal";
		#clock-cells = <0>;
	};
};