arm64: dts: qcom: sc8280xp-pmics: add pmk8280 sdam nvram

Add one of the PMK8280 SDAM blocks which can be used to store an RTC
offset.

Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230202155448.6715-21-johan+linaro@kernel.org