Alphascale asm9260 Watchdog timer

Required properties:

- compatible : should be "alphascale,asm9260-wdt".
- reg : Specifies base physical address and size of the registers.
- clocks : the clocks feeding the watchdog timer. See clock-bindings.txt
- clock-names : should be set to
	"mod" - source for tick counter.
	"ahb" - ahb gate.
- resets : phandle pointing to the system reset controller with
	line index for the watchdog.
- reset-names : should be set to "wdt_rst".

Optional properties:
- timeout-sec : shall contain the default watchdog timeout in seconds,
	if unset, the default timeout is 30 seconds.
- alphascale,mode : three modes are supported
	"hw" - hw reset (default).
	"sw" - sw reset.
	"debug" - no action is taken.

Example:

watchdog0: watchdog@80048000 {
	compatible = "alphascale,asm9260-wdt";
	reg = <0x80048000 0x10>;
	clocks = <&acc CLKID_SYS_WDT>, <&acc CLKID_AHB_WDT>;
	clock-names = "mod", "ahb";
	interrupts = <55>;
	resets = <&rst WDT_RESET>;
	reset-names = "wdt_rst";
	timeout-sec = <30>;
	alphascale,mode = "hw";
};