frameworks: Fix to remove noise while playing ringtone notification.

-The Mixer thread keeps buffering PCM data till 4096 bytes to render.
In ogg vorbis the frame size varies and most of the time the frame size is
512 bytes. In this there will be 8 iterations for the mixer thread to fill the
PCM data of 4096 and inbetween when there is no data recievied the mixer thread
will go into sleep of 20ms and keeps looping.
-Change has been done to reduce this looping by providng more decoded data to the
mixer buffer which will improve performance.
-Now Vobis player will provide 4 decoded frames(takes only few ms) at a time to
mixer buffer with maximum frame size being 4096 bytes.

CRs-Fixed: 212278