h264_refs: Do not print check_opcodes() return value

The return value provides no useful information and removing the printing
avoids the following warning:
libavcodec/h264_refs.c:788:15: warning: 'i' may be used uninitialized in this function [-Wuninitialized]

libavcodec/h264_refs.c

@@ -784,10 +784,10 @@ int ff_h264_decode_ref_pic_marking(H264Context *h, GetBitContext *gb,
         h->mmco_index = mmco_index;
     } else if (!first_slice && mmco_index >= 0 &&
                (mmco_index != h->mmco_index ||
-                (i = check_opcodes(h->mmco, mmco_temp, mmco_index)))) {
+                check_opcodes(h->mmco, mmco_temp, mmco_index))) {
         av_log(h->avctx, AV_LOG_ERROR,
-               "Inconsistent MMCO state between slices [%d, %d, %d]\n",
-               mmco_index, h->mmco_index, i);
+               "Inconsistent MMCO state between slices [%d, %d]\n",
+               mmco_index, h->mmco_index);
         return AVERROR_INVALIDDATA;
     }