avformat/isom: fix mix of declaration and statement

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

libavformat/isom.c

@@ -460,11 +460,12 @@ static int mov_rewrite_dvd_sub_extradata(AVStream *st)
     char buf[256];
     int pal_s_pos = 0;
     uint8_t *src = st->codec->extradata;
+    int i;
 
     if (st->codec->extradata_size != 64)
         return 0;
 
-    for (int i = 0; i < 16; i++) {
+    for (i = 0; i < 16; i++) {
         uint32_t yuv = AV_RB32(src + i * 4);
         uint32_t rgba = yuv_to_rgba(yuv);