arm64: dts: qcom: sa8775p: add the watchdog node

Now that the hypervisor issue is fixed, we can add the watchdog node
for sa8775p platforms.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230427161218.201828-1-brgl@bgdev.pl