hwc: Add target specific checks in hwcomposer

* Mdss driver supports DMA-Multiplexing on wb interface
for certain targets. Add overlay get function to query
this info during pipe allocation for wb.

* UI Scaling on external is not supported on certain
targets due to the lack of availability of pipes with
scalars. Add overlay get function to query this info
to disable action-safe calcs, DRC and others which
require downscaling.

Change-Id: I1726caa4634f72d781561e797078648524ea2eef
diff --git a/libexternal/external.cpp b/libexternal/external.cpp
index b08c0c1..98a22cd 100644
--- a/libexternal/external.cpp
+++ b/libexternal/external.cpp
@@ -34,7 +34,6 @@
 #include "external.h"
 #include "overlayUtils.h"
 #include "overlay.h"
-#include "mdp_version.h"
 #include "qd_utils.h"
 
 using namespace android;
@@ -586,7 +585,7 @@
         mHwcContext->dpyAttr[HWC_DISPLAY_EXTERNAL].xres = width;
         mHwcContext->dpyAttr[HWC_DISPLAY_EXTERNAL].yres = height;
         mHwcContext->dpyAttr[HWC_DISPLAY_EXTERNAL].mDownScaleMode = false;
-        if(!qdutils::MDPVersion::getInstance().is8x26()
+        if(mHwcContext->mOverlay->isUIScalingOnExternalSupported()
                 && mHwcContext->mMDPDownscaleEnabled) {
             int priW = mHwcContext->dpyAttr[HWC_DISPLAY_PRIMARY].xres;
             int priH = mHwcContext->dpyAttr[HWC_DISPLAY_PRIMARY].yres;