libdmabufheap: Make libdmabufheap threadsafe am: cff13da60c am: 7791798ca8

Original change: https://android-review.googlesource.com/c/platform/system/memory/libdmabufheap/+/1634146

Change-Id: I1f78ff544c4687634ae957600ea5b72f82c0beb8
tree: b2665a324955851a2bd162e6cfc0fa669be0574d
  1. include/
  2. tests/
  3. Android.bp
  4. BufferAllocator.cpp
  5. BufferAllocatorWrapper.cpp