hello_audio: Added VORBIS decoding

Fixed a bug in MP3 setup but it did not help:
mp3.nSize = sizeof(OMX_AUDIO_PARAM_PORTDEFINITIONTYPE
should be          OMX_AUDIO_PARAM_MP3TYPE

Tried also with VORBIS encoding but same effect.

Only when coding type is set to PCM audio_decode seems to be
working.