dt-bindings: watchdog: Add Realtek RTD1295

Realtek RTD1295 Watchdog

========================

Required properties:

- compatible :  Should be "realtek,rtd1295-watchdog"

- reg        :  Specifies the physical base address and size of registers

- clocks     :  Specifies one clock input

Example:

	watchdog@98007680 {

		compatible = "realtek,rtd1295-watchdog";

		reg = <0x98007680 0x100>;

		clocks = <&osc27M>;

	};