vivo: convert to new channel layout API

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

libavformat/vivo.c

@@ -249,7 +249,7 @@ static int vivo_read_header(AVFormatContext *s)
     ast->start_time        = 0;
     ast->codecpar->codec_tag  = 0;
     ast->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
-    ast->codecpar->channels = 1;
+    ast->codecpar->ch_layout.nb_channels = 1;
 
     return 0;
 }