D2H and H2D unpinned memory transfer support

Change-Id: If6d6c970f435e5d917d5cc6cddc2ee2918cd1c37

Conflicts:
	src/hip_hcc.cpp

include/hcc_detail/hip_hcc.h

@@ -606,7 +606,7 @@ public: // Data, set at initialization:
     unsigned                _compute_units;
 
     StagingBuffer           *_staging_buffer[2]; // one buffer for each direction.
-
+    int                     isLargeBar;
 
     unsigned                _device_flags;