ffmpeg: Fix variable collisions

 * We need some undefs here because FFMPEG wants these values to equal
   either 1 or 0, while Bionic just defines it to nothing.

Change-Id: I2505d4c077db41b3fa61af5a9b2c83491f0b9b88
Merge remote-tracking branch 'cm/cm-12.0' into cm-12.0