libmeminfo: add GPU total memory usage query function am: 5106ef712c am: ae9bdafc2a

Original change: https://android-review.googlesource.com/c/platform/system/memory/libmeminfo/+/1472486

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I3c8eb232403af1a532a80f12494da4332730edbb