libgralloc: Suppress "using old API" warnings

While 4.3 blobs are functional without issues, they cause massive
qdmemalloc spam.  The commit that put this code in indicates that
there is full backwards compatibility, so allow the spam to be disabled.

Change-Id: Id635bfa1a146c3fd95ced1a425498c8b985fc049
Merge pull request #1 from omnirom/android-4.4

libgralloc: Suppress "using old API" warnings