Mediatek SoCs Watchdog timer

The watchdog supports a pre-timeout interrupt that fires timeout-sec/2
before the expiry.

Required properties:

- compatible should contain:
	"mediatek,mt2701-wdt", "mediatek,mt6589-wdt": for MT2701
	"mediatek,mt2712-wdt": for MT2712
	"mediatek,mt6589-wdt": for MT6589
	"mediatek,mt6797-wdt", "mediatek,mt6589-wdt": for MT6797
	"mediatek,mt7622-wdt", "mediatek,mt6589-wdt": for MT7622
	"mediatek,mt7623-wdt", "mediatek,mt6589-wdt": for MT7623
	"mediatek,mt7629-wdt", "mediatek,mt6589-wdt": for MT7629
	"mediatek,mt8183-wdt": for MT8183
	"mediatek,mt8516-wdt", "mediatek,mt6589-wdt": for MT8516
	"mediatek,mt8192-wdt": for MT8192
	"mediatek,mt8195-wdt", "mediatek,mt6589-wdt": for MT8195

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

Optional properties:
- interrupts: Watchdog pre-timeout (bark) interrupt.
- timeout-sec: contains the watchdog timeout in seconds.
- #reset-cells: Should be 1.

Example:

watchdog: watchdog@10007000 {
	compatible = "mediatek,mt8183-wdt",
		     "mediatek,mt6589-wdt";
	reg = <0 0x10007000 0 0x100>;
	interrupts = <GIC_SPI 139 IRQ_TYPE_NONE>;
	timeout-sec = <10>;
	#reset-cells = <1>;
};