all: Don't set AVClass.item_name to its default value

Unnecessary since acf63d5350adeae551d412db699f8ca03f7e76b9;
also avoids relocations.

Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavformat/dfpwmdec.c

@@ -81,7 +81,6 @@ static const AVOption dfpwm_options[] = {
 };
 static const AVClass dfpwm_demuxer_class = {
     .class_name = "dfpwm demuxer",
-    .item_name  = av_default_item_name,
     .option     = dfpwm_options,
     .version    = LIBAVUTIL_VERSION_INT,
 };