hwc: Fix right mixer layer positioning.

Fix positioning of layer on the right mixer, by making it relative to
the half width of total panel.

Change-Id: Iecbe4496db1faae426b2606118ccaab90c1e4fca
diff --git a/libhwcomposer/hwc_utils.cpp b/libhwcomposer/hwc_utils.cpp
index 746f0c3..3bbed7c 100644
--- a/libhwcomposer/hwc_utils.cpp
+++ b/libhwcomposer/hwc_utils.cpp
@@ -855,8 +855,8 @@
     if(rDest != OV_INVALID) {
         PipeArgs pargR(mdpFlagsR, whf, z, isFg,
                 static_cast<eRotFlags>(rotFlags));
-        tmp_dstR.right = tmp_dstR.right - tmp_dstR.left;
-        tmp_dstR.left = 0;
+        tmp_dstR.right = tmp_dstR.right - hw_w/2;
+        tmp_dstR.left = tmp_dstR.left - hw_w/2;
         if(configMdp(ctx->mOverlay, pargR, orient,
                 tmp_cropR, tmp_dstR, metadata, rDest) < 0) {
             ALOGE("%s: commit failed for right mixer config", __FUNCTION__);