drm/msm/dsi: dsi_host: drop unused clocks

Several source clocks are not used anymore, so stop handling them.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Patchwork: https://patchwork.freedesktop.org/patch/542558/
Link: https://lore.kernel.org/r/20230614224402.296825-1-dmitry.baryshkov@linaro.org