avcodec/utils: only warn when passed invalid lowres value

This makes it easier to use the lowres option when dealing with input
files in different codecs. If the codec doesn't support lowres=1 for
instance, it will throw a warning and use lowres=0 instead of erroring
out completely.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/utils.c

@@ -1389,10 +1389,9 @@ int attribute_align_arg avcodec_open2(AVCodecContext *avctx, const AVCodec *code
         avctx->thread_count = 1;
 
     if (avctx->codec->max_lowres < avctx->lowres || avctx->lowres < 0) {
-        av_log(avctx, AV_LOG_ERROR, "The maximum value for lowres supported by the decoder is %d\n",
+        av_log(avctx, AV_LOG_WARNING, "The maximum value for lowres supported by the decoder is %d\n",
                avctx->codec->max_lowres);
-        ret = AVERROR(EINVAL);
-        goto free_and_end;
+        avctx->lowres = avctx->codec->max_lowres;
     }
 
 #if FF_API_VISMV