Merge https://source.denx.de/u-boot/custodians/u-boot-watchdog

CI: https://dev.azure.com/sr0718/u-boot/_build/results?buildId=378&view=results

* watchdog: gpio_wdt: add support for stoppable devices (Rasmus)
* watchdog: Add DaVinci's watchdog support (Bastien)
* cyclic: disentangling cyclic API from schedule() (Rasmus)
* watchdog: introduce separate SPL symbol for WDT_GPIO (Rasmus)