overlay: Add FB flag for UI mirroring

When the source for rotator is the
framebuffer, the FB flag needs to be set
to identify the type of memory to be used.

Change-Id: I4fc6112832ad42eb7092be5243653b9baf8a241a

liboverlay/overlayLib.cpp

@@ -1489,6 +1489,9 @@ bool OverlayDataChannel::mapRotatorMemory(int num_buffers, bool uiChannel, int r
             }
         }
     }
+    // Set this flag if source memory is fb
+    if(uiChannel)
+        mRotData.src.flags |= MDP_MEMORY_ID_TYPE_FB;
 
     mOvDataRot.data.memory_id = mPmemFD;
     mRotData.dst.memory_id = mPmemFD;