This filter only had an AVClass and empty options because up until
recently, avfilter_init_str() errored out when options were provided
for a filter without an AVClass. But setting (generic) options is
necessary to take advantage of timeline support. So with
avfilter_init_str() fixed, the AVClass and the options can be removed.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>