rtc: gemini: Augment DT bindings for Faraday

* Cortina Systems Gemini RTC

Gemini SoC real-time clock.

Required properties:

- compatible : Should be "cortina,gemini-rtc"

Examples:

rtc@45000000 {

	compatible = "cortina,gemini-rtc";

	reg = <0x45000000 0x100>;

	interrupts = <17 IRQ_TYPE_LEVEL_HIGH>;

};

* Faraday Technology FTRTC010 Real Time Clock

This RTC appears in for example the Storlink Gemini family of

SoCs.

Required properties:

- compatible : Should be one of:

  "faraday,ftrtc010"

  "cortina,gemini-rtc", "faraday,ftrtc010"

Optional properties:

- clocks: when present should contain clock references to the

  PCLK and EXTCLK clocks. Faraday calls the later CLK1HZ and

  says the clock should be 1 Hz, but implementers actually seem

  to choose different clocks here, like Cortina who chose

  32768 Hz (a typical low-power clock).

- clock-names: should name the clocks "PCLK" and "EXTCLK"

  respectively.

Examples:

rtc@45000000 {

	compatible = "cortina,gemini-rtc";

	reg = <0x45000000 0x100>;

	interrupts = <17 IRQ_TYPE_LEVEL_HIGH>;

	clocks = <&foo 0>, <&foo 1>;

	clock-names = "PCLK", "EXTCLK";

};