dt-bindings: display/msm: sc7180-dpu: Describe SM6125

dt-bindings: display/msm: sc7180-dpu: Describe SM6125

SM6125 is identical to SM6375 including the throttle clock that is also
provided to the MDP node downstream.  Note that any SoC other than
SM6375 (currently SC7180 and SM6350) has an unconstrained maximum number
of clocks and could either pass or leave out this "throttle" clock.

Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
Patchwork: https://patchwork.freedesktop.org/patch/548972/
Link: https://lore.kernel.org/r/20230723-sm6125-dpu-v4-8-a3f287dd6c07@somainline.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>