avcodec/mpeg12dec: Use skip_1stop_8data_bits()

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

libavcodec/mpeg12dec.c

@@ -1639,9 +1639,8 @@ static int mpeg_decode_slice(MpegEncContext *s, int mb_y,
     }
 
     /* extra slice info */
-    while (get_bits1(&s->gb) != 0) {
-        skip_bits(&s->gb, 8);
-    }
+    if (skip_1stop_8data_bits(&s->gb) < 0)
+        return AVERROR_INVALIDDATA;
 
     s->mb_x = 0;