Allwinner SoCs Watchdog timer

Required properties:

- compatible : should be "allwinner,<soc-family>-wdt", the currently supported
  SoC families being sun4i and sun6i
- reg : Specifies base physical address and size of the registers.

Example:

wdt: watchdog@01c20c90 {
	compatible = "allwinner,sun4i-wdt";
	reg = <0x01c20c90 0x10>;
};
