arm64: dts: qcom: pmk8350: Allow specifying arbitrary SID

PMK8350 is shipped on SID6 with some SoCs, for example with SM6375.
Add some preprocessor logic to allow changing the SID in cases like
this.

While I am not in favour of adding #if's into the device tree, this
is the least messy way to handle this. If one isn't specified, it
will default to 0 (as it has been previously).

Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221115152727.9736-3-konrad.dybcio@linaro.org