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/libvirtual/virtual.cpp b/libvirtual/virtual.cpp
index bed5e4c..1f8e70c 100644
--- a/libvirtual/virtual.cpp
+++ b/libvirtual/virtual.cpp
@@ -47,7 +47,6 @@
 #include "virtual.h"
 #include "overlayUtils.h"
 #include "overlay.h"
-#include "mdp_version.h"
 #include "qd_utils.h"
 
 using namespace android;
@@ -184,7 +183,7 @@
 
         initResolution(extW, extH);
 
-        if(!qdutils::MDPVersion::getInstance().is8x26()
+        if(mHwcContext->mOverlay->isUIScalingOnExternalSupported()
                 && (mHwcContext->mMDPDownscaleEnabled || isDRC)) {
 
             // maxArea represents the maximum resolution between