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: 865ff2e6 ("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.orgSigned-off-by: Bjorn Andersson <andersson@kernel.org>