avcodec/mpeg4video: Reorder operations to reduce accesses to err_recognition

About 9 cpu cycle faster mpeg4_decode_mb()
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mpeg4video.h

@@ -230,21 +230,21 @@ static inline int ff_mpeg4_pred_dc(MpegEncContext *s, int n, int level,
     } else {
         level += pred;
         ret    = level;
-        if (s->avctx->err_recognition & (AV_EF_BITSTREAM | AV_EF_AGGRESSIVE)) {
+    }
+    level *= scale;
+    if (level & (~2047)) {
+        if (!s->encoding && (s->avctx->err_recognition & (AV_EF_BITSTREAM | AV_EF_AGGRESSIVE))) {
             if (level < 0) {
                 av_log(s->avctx, AV_LOG_ERROR,
                        "dc<0 at %dx%d\n", s->mb_x, s->mb_y);
                 return -1;
             }
-            if (level * scale > 2048 + scale) {
+            if (level > 2048 + scale) {
                 av_log(s->avctx, AV_LOG_ERROR,
                        "dc overflow at %dx%d\n", s->mb_x, s->mb_y);
                 return -1;
             }
         }
-    }
-    level *= scale;
-    if (level & (~2047)) {
         if (level < 0)
             level = 0;
         else if (!(s->workaround_bugs & FF_BUG_DC_CLIP))