CameraService: Decouple dequeue and lock

Decouple lockBuffer from dequeueBuffer. Add lock_buffer to preview_stream_ops,
so HALs will be fully in charge of managing buffers.

Change-Id: I7b53487d618bdf08ba904c5a0f41af462a7ca773
Signed-off-by: Iliyan Malchev <malchev@google.com>
1 file changed