display: Fix Bug in 180 degree rotation use case for 4kx2k panel.

Check NULL condition for pointer to rotator object to swap
configuration information between right and left mixer.

Change-Id: Ib23552efcb7807164a33f618f7ff41c469661cb5
diff --git a/libhwcomposer/hwc_utils.cpp b/libhwcomposer/hwc_utils.cpp
index 4f87ac4..bd0b4a6 100644
--- a/libhwcomposer/hwc_utils.cpp
+++ b/libhwcomposer/hwc_utils.cpp
@@ -822,7 +822,7 @@
     //Not needed if the layer is confined to one half of the screen.
     //If rotator has been used then it has also done the flips, so ignore them.
     if((orient & OVERLAY_TRANSFORM_FLIP_V) && lDest != OV_INVALID
-            && rDest != OV_INVALID && rot == NULL) {
+            && rDest != OV_INVALID && (*rot) == NULL) {
         hwc_rect_t new_cropR;
         new_cropR.left = tmp_cropL.left;
         new_cropR.right = new_cropR.left + (tmp_cropR.right - tmp_cropR.left);