drm/msm/sde: Decrese PPB Dither strength

While playing HDR, PPB dither is stronger than we expected.
Change configuration so that the strength is normal.

Change-Id: Iae179a8c6eb0b75508284e29f1c0ef4f85e80846
Signed-off-by: Lakshmi Narayana Kalavala <lkalaval@codeaurora.org>
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>