stagefright: fix block model operations for OMX codecs

- Handle linear buffers larger than OMX buffers
- Handle graphic buffers
- Fix encrypted decoding use case

Bug: 157528365
Test: atest CtsMediaTestCases:MediaCodecBlockModelTest
Test: atest CtsMediaTestCases -- --module-arg CtsMediaTestCases:size:small
Change-Id: Ibd553ccf0aee054f2cf43be216527e2712fe859d