Cadence Real Time Clock

The Cadence RTC controller with date, time and alarm capabilities.
The alarm may wake the system from low-power state.

Required properties:
- compatible: Should be "cdns,rtc-r109v3"
- reg: Specifies base physical address and size of the register area.
- interrupts: A single interrupt specifier.
- clocks: Must contain two entries:
	- pclk: APB registers clock
	- ref_clk: reference 1Hz or 100Hz clock, depending on IP configuration
	See ../clocks/clock-bindings.txt for details.

Example:
        rtc0: rtc@fd080000 {
        	compatible = "cdns,rtc-r109v3";
        	reg = <0xfd080000 0x1000>;

        	clock-names = "pclk", "ref_clk";
        	clocks = <&sysclock>, <&refclock>;

        	interrupt-parent = <&gic>;
        	interrupts = <0 6 IRQ_TYPE_LEVEL_HIGH>;
        };