libdmabufheap: Do not open heap device in RW mode am: 14dd34138d am: 5ca1d33e78 am: b8de47d231

Original change: https://android-review.googlesource.com/c/platform/system/memory/libdmabufheap/+/1429195

Change-Id: I0a9705e8c368a7e10e2aa49d621642f3c5412487
tree: 36a632ea79d5b52de4a29d44abcc0db4ed237955
  1. include/
  2. tests/
  3. Android.bp
  4. BufferAllocator.cpp
  5. BufferAllocatorWrapper.cpp