dt-bindings: soc: qcom: qcom,smd-rpm: Add a compatible for SM6375

Document the compatible for SM6375.

Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220921004534.151990-1-konrad.dybcio@somainline.org