libavformat/argo_brp: fix incorrect ASF chunk header read

Was inadvertently broken in the switch to ffio_read_size().

Fixes: 6dd83fab44

PR: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21650

Reviewed-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Signed-off-by: Zane van Iperen <zane@zanevaniperen.com>

libavformat/argo_brp.c

@@ -309,7 +309,7 @@ static int argo_brp_read_header(AVFormatContext *s)
         if (blk.size < ASF_CHUNK_HEADER_SIZE)
             return AVERROR_INVALIDDATA;
 
-        ret = ffio_read_size(pb, buf, BRP_BLOCK_HEADER_SIZE);
+        ret = ffio_read_size(pb, buf, ASF_CHUNK_HEADER_SIZE);
         if (ret < 0)
             return ret;