arm64: dts: qcom: sm6375: Bump CPU rail power collapse index

In preparation for supporting a less-deep sleep state, rename the
existing rail power off from _0 to _1.

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-v2-12-708b8191f7eb@linaro.org