arm64: dts: qcom: sc8280xp: Set status = "reserved" on PSHOLD

arm64: dts: qcom: sc8280xp: Set status = "reserved" on PSHOLD

On most devices, TZ seems to be blocking access to the PSHOLD reboot
register. This seems to be TZ, as even kicking the hypervisor doesn't
seem to make it writable.

Fixes: 865ff2e6f5da ("arm64: dts: qcom: sc8280xp: Add PS_HOLD restart")
Reported-by: Steev Klimaszewski <steev@kali.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Tested-by: Steev Klimaszewski <steev@kali.org>
Link: https://lore.kernel.org/r/20240510-topic-8280_off-v1-1-bcc70cda449e@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>