Move ReadDmaBufs() into dmabufinfo.cpp am: 3e598e47d9 am: 3e0496da85

Original change: https://android-review.googlesource.com/c/platform/system/memory/libmeminfo/+/2010716

Change-Id: I7c47c308aed360dfe8b6b5c9ef1ee6785c584525