avformat/dashdec: propagate icy to child AVIOContexts

When the user decides they do not want to to send the Icy-MetaData
header, this should be respected for all requests, not just the first
one.

Fix #5578
Reviewed-by: Liu Steven <lq@chinaffmpeg.org>
Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/dashdec.c

@@ -1851,7 +1851,7 @@ static int save_avio_options(AVFormatContext *s)
 {
     DASHContext *c = s->priv_data;
     const char *opts[] = {
-        "headers", "user_agent", "cookies", "http_proxy", "referer", "rw_timeout", NULL };
+        "headers", "user_agent", "cookies", "http_proxy", "referer", "rw_timeout", "icy", NULL };
     const char **opt = opts;
     uint8_t *buf = NULL;
     int ret = 0;