stagefright: AwesomePlayer: restrict early-queueing of buffers to > 30fps

Queueing early-frames helps absorb scheduling jitters and is desirable
for high-framerate content. However, for sub-30fps, this simply
seems to increase display-updates. Queue early selectively for >30fps.

Change-Id: Icb9d299a8b90457f0b5e0ac7d4d4d5942caafb90
CRs-Fixed: 712504