multimedia/ffmpeg: enable SVTAV1 on non-amd64 after ddd35eebbc90

$ ab-av1 auto-encode -i foo.mp4
Encoding foo.av1.mp4

Searching 00:00:00 ################## (sampling crf 32, eta 0s)

Error: ffmpeg encode_sample exit code Some(1)

https://github.com/alexheretic/ab-av1/commit/f61a244bd64f