12l: Fix compilation with --disable-vdpau.

Originally committed as revision 16630 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpeg12.c

@@ -2313,7 +2313,7 @@ static int decode_chunks(AVCodecContext *avctx,
                         s2->error_count += s2->thread_context[i]->error_count;
                 }
 
-                if (avctx->codec->capabilities&CODEC_CAP_HWACCEL_VDPAU)
+                if (CONFIG_MPEG_VDPAU_DECODER && avctx->codec->capabilities&CODEC_CAP_HWACCEL_VDPAU)
                     ff_vdpau_mpeg_picture_complete(s2, buf, buf_size, s->slice_count);
 
                 if (slice_end(avctx, picture)) {