dt-bindings: display: msm: dsi-controller-main: restore assigned-clocks

Restore the assgined-clocks and assigned-clock-parents properties that
were lost during the txt -> YAML conversion.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20210709210729.953114-2-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>