dt-bindings: mfd: da9062: Correct file name for watchdog

Replace the watchdog file name with the name currently in use.

Signed-off-by: Christoph Niedermaier <cniedermaier@dh-electronics.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20221130101426.5318-1-cniedermaier@dh-electronics.com