Wi2Wi W2SG0004 GPS module connected through UART

Should be a subnode of the SoC UART it is connected to.

Required properties:
- compatible:	must be
	"wi2wi,w2sg0004"
- enable-gpio:	the GPIO that controls the module's power toggle
	input. A positive impulse of sufficent length toggles the
	power state.

Optional properties:
- lna-supply:	an (optional) LNA regulator that is enabled together with the GPS receiver

Example:

&uart2 {
	w2sg0004: gps {
		compatible = "wi2wi,w2sg0004";
		lna-supply = <&vsim>;   /* LNA regulator */
		enable-gpios = <&gpio5 17 GPIO_ACTIVE_HIGH>;    /* GPIO_145: trigger for turning on/off w2sg0004 */
        };
};
