Allows run-time control over watchdog auto-start and the timeout via
setting the environment variable watchdog_timeout_ms. A value of zero
means "do not start". Use CONFIG_WATCHDOG_TIMEOUT_MSECS as initial value.
Users can enable the watchdog to monitor the boot process until userspace
or OS takes over to serve the watchdog.
Signed-off-by: Wadim Egorov <w.egorov@phytec.de>
