avformat/cavsvideodec: Fix probing when the file extension is avs

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 52e563bb2f)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/cavsvideodec.c

@@ -61,7 +61,7 @@ static int cavsvideo_probe(AVProbeData *p)
         }
     }
     if(seq && seq*9<=pic*10)
-        return AVPROBE_SCORE_EXTENSION;
+        return AVPROBE_SCORE_EXTENSION+1;
     return 0;
 }