Allwinner sun4i Watchdog timer

Required properties:

- compatible : should be "allwinner,sun4i-wdt"
- reg : Specifies base physical address and size of the registers.

Example:

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