mpeg: Suppress a compiler warning on callback type

libavformat/mpegenc.c

@@ -850,7 +850,8 @@ static int flush_packet(AVFormatContext *ctx, int stream_index,
         /* output data */
         assert(payload_size - stuffing_size <= av_fifo_size(stream->fifo));
         av_fifo_generic_read(stream->fifo, ctx->pb,
-                             payload_size - stuffing_size, &avio_write);
+                             payload_size - stuffing_size,
+                             (void (*)(void*, void*, int))avio_write);
         stream->bytes_to_iframe -= payload_size - stuffing_size;
     } else {
         payload_size  =