Rockchip rk timer RTC

Required properties:
- compatible: should be:
  "rockchip,rk3308-timer-rtc": for Rockchip RK3308
- reg: base address of the timer register and length of memory mapped region.
- interrupts: should contain the interrupts for the timer
- clocks : must contain an entry for each entry in clock-names
- clock-names : must include the following entries:
  "timer", "pclk"

Example:
	rk_timer_rtc: rk-timer-rtc@ff1a0020 {
		compatible = "rockchip,rk3308-timer-rtc";
		reg = <0x0 0xff1a0020 0x0 0x20>;
		interrupts = <GIC_SPI 26 IRQ_TYPE_LEVEL_HIGH>;
		clocks = <&cru PCLK_TIMER>, <&cru SCLK_TIMER1>;
		clock-names = "pclk", "timer";
	};