msm8974: Temporarily disable partial display updates

 * We have a recent issue where a single (arbitrary) line
   of the display very rarely turns black, and no on-demand
   reproduction case for it yet.  Wonderful, isn't it?
 * Since much of the recent work was done in order to
   support this feature, let's turn it off for awhile
   to (at the very least) eliminate it as a cause.
 * This will be back after more testing / debugging, as
   it provides a great performance boost as well as
   reducing power consumption.

Change-Id: I37fa998865235b6a6e1567cd8c8ac66b651de6a5