[AML] HEVC, S805 and S812 board support

This PR depends on #5374 (needs BitstreamConverter patch for HEVC).

HEVC using AMLCodec is working on all sample files I could get. Need more interested testers :)

Also, I did not change h264 way of using bitstreamconverter for now, not to mess anything.

@koying @davilla 
Could you elaborate on what's the use of m_hevc?