dt-bindings: display/msm: sc7180-dpu: Describe SM6350 and SM6375

SC7180, SM6350 and SM6375 use a rather similar hw setup for DPU, with
the main exception being that the last one requires an additional
throttle clock.

It is not well understood yet, but failing to toggle it on makes the
display hardware stall and not output any frames.

Document SM6350 and SM6375 DPU.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/541283/
Link: https://lore.kernel.org/r/20230411-topic-straitlagoon_mdss-v6-3-dee6a882571b@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>