arm64: dts: qcom: sc8280xp: Add PS_HOLD restart

Killing the platform with a single write and no firmware involvement is
pretty cool, add support for it.

Note that due to restart notifier priority settings, PSCI reset will
be used instead, unless:

a) PSCI is not exposed by the firmware (e.g. because the fw was replaced)
or
b) PSCI restart fails for some reason

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20240307-topic-8280_nodes-v1-3-4eba20e08902@linaro.org


Signed-off-by: Bjorn Andersson <andersson@kernel.org>