lavf/vplayerdec: Improve auto-detection.

Fixes the incorrect detection of 16_selma_OneFrame_QP39.yuv (gray16le
rawvideo) as vplayer format.
(cherry picked from commit 77726d32a8)

libavformat/vplayerdec.c

@@ -36,8 +36,8 @@ static int vplayer_probe(AVProbeData *p)
     char c;
     const unsigned char *ptr = p->buf;
 
-    if ((sscanf(ptr, "%*d:%*d:%*d.%*d%c", &c) == 1 ||
-         sscanf(ptr, "%*d:%*d:%*d%c",     &c) == 1) && strchr(": =", c))
+    if ((sscanf(ptr, "%*3d:%*2d:%*2d.%*2d%c", &c) == 1 ||
+         sscanf(ptr, "%*3d:%*2d:%*2d%c",      &c) == 1) && strchr(": =", c))
         return AVPROBE_SCORE_MAX;
     return 0;
 }