libstagefright: Fix a video lag bug after audio reached EOS.

http://git.insignal.co.kr/samsung/exynos/android/platform/frameworks/av/commit/?h=exynos-jb&id=da4104e5f934633b4ba7fda06bc9ef3ba0f85a31

Change-Id: I84ee5d8de1288eab99400b9fb84557040ce7bda5
Author: Yunji Kim