dt-bindings: iio: qcom: adc7-pm8350: Allow specifying SID for channels

As per the new ADC7 architecture used by the Qualcomm PMICs, each PMIC
has the static Slave ID (SID) assigned by default. The primary PMIC
PMK8350 is responsible for collecting the temperature/voltage data from
the slave PMICs and exposing them via it's registers.

For getting the measurements from the slave PMICs, PMK8350 uses the
channel ID encoded with the SID of the relevant PMIC. So far, the
dt-binding for the slave PMIC PM8350 assumed that there will be only
one PM8350 in a system. So it harcoded SID 1 with channel IDs.

But this got changed in platforms such as Lenovo X13s where there are a
couple of PM8350 PMICs available. So to address multiple PM8350s, change
the binding to accept the SID specified by the user and use it for
encoding the channel ID.

It should be noted that, even though the SID is static it is not
globally unique. Only the primary PMIC has the unique SID id 0.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221103095810.64606-2-manivannan.sadhasivam@linaro.org