stagefright: add an extra buffer to ANW's BUfferQueue

Add an extra buffer to ensure video player has a free buffer to
dequeue rather than wait for the queued buffer to be displayed.
Enable logs to indicate number of buffers allocated.

NOTE: This is not needed for 30fps content on 60fps panel, But
making this change regardless for all framerates till root-cause
is identified in SF

Change-Id: Id1048d7a104b2a75613dda8b9cf166e59bc4bb04