MOXA ART real-time clock

Required properties:

- compatible : Should be "moxa,moxart-rtc"
- gpio-rtc-sclk : RTC sclk gpio, with zero flags
- gpio-rtc-data : RTC data gpio, with zero flags
- gpio-rtc-reset : RTC reset gpio, with zero flags

Example:

	rtc: rtc {
		compatible = "moxa,moxart-rtc";
		gpio-rtc-sclk = <&gpio 5 0>;
		gpio-rtc-data = <&gpio 6 0>;
		gpio-rtc-reset = <&gpio 7 0>;
	};