avcodec/mpegvideo: Ignore skip_idct for encoders

It is documented to be unused for encoders.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavcodec/mpegvideo.c

@@ -1413,7 +1413,6 @@ void mpv_reconstruct_mb_internal(MpegEncContext *s, int16_t block[12][64],
                         ff_mpv_motion(s, dest_y, dest_cb, dest_cr, 1, s->next_picture.f->data, op_pix, op_qpix);
                     }
                 }
-            }
 
             /* skip dequant / idct if we are really late ;) */
             if(s->avctx->skip_idct){
@@ -1422,6 +1421,7 @@ void mpv_reconstruct_mb_internal(MpegEncContext *s, int16_t block[12][64],
                    || s->avctx->skip_idct >= AVDISCARD_ALL)
                     goto skip_idct;
             }
+            }
 
             /* add dct residue */
             if (IS_ENCODER(s) || !(IS_MPEG12(s) || s->msmpeg4_version