arm64: dts: qcom: pm8916: Add PON watchdog node

Add watchdog child node to the PM8916 PON device.

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>