arm64: dts: qcom: sm6375: Introduce C3 power state for both ARM clusters

Introduce the C3 power state, which - to the best of my understanding -
gates the CPU clock, but does not shut off the power rail.

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230303-topic-sm6375_features0_dts-v2-13-708b8191f7eb@linaro.org