[DRIVER][WDT] add SECO GPIO watchdog driver
This is a generic driver for GPIO-based WDTs that use two GPIOs: enable and trigger. It is based on the linux GPIO-controlled watchdog driver.
There exists another SECO driver that can be used for similar hardware, having the compatible name "seco,apx-wdog": that one initializes the watchdog earlier in the boot process, and so is used if that more complex use case is necessary.
Imported from https://git.seco.com/edgehog/bsp/nxp/linux-seco-imx/-/commit/3ab6e6e5daa1955d3acc6aee41aab5712744c7e1