Require at least three frames to autodetect loas.

(cherry picked from commit a60530e3ee)

libavformat/loasdec.c

@@ -55,7 +55,6 @@ static int loas_probe(AVProbeData *p)
     if   (first_frames>=3) return AVPROBE_SCORE_MAX/2+1;
     else if(max_frames>100)return AVPROBE_SCORE_MAX/2;
     else if(max_frames>=3) return AVPROBE_SCORE_MAX/4;
-    else if(max_frames>=1) return 1;
     else                   return 0;
 }