hwc: Partial Update for MDP3 targets

Enable partial update for MDP3 targets.
Use computed ROI of mdpcomp in copybit
to avoid composition of layers outside ROI.

Change-Id: I4b23fd48cac814f8c35a3c01253dca8c297036f9
diff --git a/libhwcomposer/hwc_mdpcomp.h b/libhwcomposer/hwc_mdpcomp.h
index 268e9aa..3ed9186 100644
--- a/libhwcomposer/hwc_mdpcomp.h
+++ b/libhwcomposer/hwc_mdpcomp.h
@@ -262,6 +262,8 @@
     static bool sEnableYUVsplit;
     bool mModeOn; // if prepare happened
     bool allocSplitVGPipesfor4k2k(hwc_context_t *ctx, int index);
+    //Enable Partial Update for MDP3 targets
+    static bool enablePartialUpdateForMDP3;
 };
 
 class MDPCompNonSplit : public MDPComp {