Revert "slim: Build stagefright ffmpeg plugin"

* Stop Building ffmpeg pulgin until it gets fixed
This reverts commit 76f7bccf0a8a0d5915f064e0e847cb4cab9b26c1.
Change-Id: I23d50a299bee724ab523723a12df6cd1ff0f3a1a
Merge "Revert "slim: Build stagefright ffmpeg plugin"" into lp5.0