avformat/uncodedframecrc: fix incompatible pointer type warning

Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/uncodedframecrcenc.c

@@ -119,6 +119,11 @@ static void audio_frame_cksum(AVBPrint *bp, AVFrame *frame)
     }
 }
 
+static int write_header(struct AVFormatContext *s)
+{
+    return ff_framehash_write_header(s, 1);
+}
+
 static int write_frame(struct AVFormatContext *s, int stream_index,
                        AVFrame **frame, unsigned flags)
 {
@@ -164,7 +169,7 @@ AVOutputFormat ff_uncodedframecrc_muxer = {
     .long_name         = NULL_IF_CONFIG_SMALL("uncoded framecrc testing"),
     .audio_codec       = AV_CODEC_ID_PCM_S16LE,
     .video_codec       = AV_CODEC_ID_RAWVIDEO,
-    .write_header      = ff_framehash_write_header,
+    .write_header      = write_header,
     .write_packet      = write_packet,
     .write_uncoded_frame = write_frame,
     .flags             = AVFMT_VARIABLE_FPS | AVFMT_TS_NONSTRICT |