ffmpeg: bump to version 2.8

0016-ranlib.patch is not needed anymore since the problem that it fixes
is already handled upstream:

  https://github.com/FFmpeg/FFmpeg/commit/2c77ca459e9c9aceee5ed93f8dd8de09e9fbf8df



Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>