VR: Update VR HWC to use buffer metadata passed by SurfaceFlinger

Without gralloc1 support, need to pass buffer metadata in order to
import native buffers and used them as graphic buffers.

Bug: 36481301
Test: Compiled and ran on device; Verified VR Window Manager properly
displays SurfaceFlinger buffers.

Change-Id: I8426be1d79dcc2fbd631c399427ae03cb2afc21d