drm/msm/dsi: Uncomment core_mmss clock for MSM8996

The MSM8996 core_mmss clock was commented out due to some
strange issues that others were experiencing.

At least SONY Tone family is working perfectly fine with this clock
declared and gets it up and running without any error.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Link: https://lore.kernel.org/r/20210228124328.136397-1-konrad.dybcio@somainline.org


Signed-off-by: Rob Clark <robdclark@chromium.org>