avformat/mov: Break out of inner loop early in mov_estimate_video_delay()

0.266 <- 0.299 sec (this is time ffmpeg so containing alot other things)

Sample for benchmark was: ffmpeg -f rawvideo -pix_fmt yuv420p -s 32x32 -i /dev/zero -t 24:00:00.00 out.mp4

Reviewed-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Reviewed-by: Sasi Inguva <isasi@google.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit aba13dc1)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>