stagefright: fix legacy support for CameraSource

- allocate big enough buffers for native metadata source even in
CameraSource mode
- don't check range when using native metadata mode (and converting
it to GrallocSource) as OMX buffer will be smaller than input
- log allocated vs. OMX reported sizes in OMXNodeInstance logs

Bug: 21708032
Change-Id: I7eeffc5116079e5b368f84980e8e7524260aaccf