NRF52 hal_watchdog_init() doesn't fulfil interface

Watchdog HAL [documentation, function *hal_watchdog_init()*](https://mynewt.apache.org/latest/os/modules/hal/hal_watchdog/hal_watchdog.html#c.hal_watchdog_init) says it **returns expiration time as positive value**.

However, [nrf52 implementation](https://github.com/apache/mynewt-core/blob/master/hw/mcu/nordic/nrf52xxx/src/hal_watchdog.c#L44) returns always 0.

Is the documentation wrong? the implementation?

// test assertion
assert(hal_watchdog_init(1000) > 0);

Start with the linked Watchdog HAL documentation and hw/mcu/nordic/nrf52xxx/src/hal_watchdog.c, then compare the documented return contract with the implementation and the assert(hal_watchdog_init(1000) > 0) example. Determine which behavior is intended and make the implementation and documentation agree, with the assertion serving as the completion check.

Written by the indexing model from the issue text.