msm: mdss: Block postprocessing updates during DTM

When calibration tool requests the fb driver to enter in
Display Tuning Mode (DTM), PostProcessing blocks should
not update the HSIC, Memory color, Six Zone colors, etc.
Updating them during DTM conflicts the update from
calibration tool.

Change-Id: I11fcac57a651581d85e771911f83b2fdd9c3c681
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>