msm: mdss: Clear pp dirty flags based on program stage

Clear PP features dirty flags only when they are programmed, based on
programming stage, i.e. clear dirty flags of features programmed in
early stage after early stage programming and clear dirty flags of
features programmed in deferred stage after their actual programming
is complete.

Clearing the flags in one go is resulting in missing programming of
features designated to be programmed in early stage, if the dirty flags
are updated in between the stages.

Change-Id: If65a5982254a7421c6f0ec32018361c651964e4e
Signed-off-by: Ch Ganesh Kumar <chganesh@codeaurora.org>