drivers: watchdog: Add Xilinx Window Watchdog driver support

Xilinx Window Watchdog driver uses window watchdog mode. Window watchdog
timer(WWDT) contains closed(first) and open(second) window with 32bit
width each. Write to the watchdog timer within predefined window periods
of time. This means a period that is not too soon and a period that is
not too late. The WWDT has to be restarted within the open window time.
If the software tries to restart WWDT outside of open window time
period, it generates a SoC reset.

Signed-off-by: Harini T <harini.t@amd.com>