package/tvheadend: revert minimum required ffmpeg version numbers

Fixes
http://autobuild.buildroot.net/results/e62/e62dd4dbdb4c92bc657936566e73388e76343903/
and many others

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
1 file changed