Pffft: Add VTS path under the visibility attribute am: 4f870d2053

Original change: https://android-review.googlesource.com/c/platform/external/pffft/+/2923853

Change-Id: I721b3945f0dc07780fb5efc1b577b40816fe924b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>