rtp: add some additional rtcp sdes values
Matches the current list at https://www.iana.org/assignments/rtp-parameters/rtp-parameters.xhtml#rtp-parameters-5 as of 2021-September.
Matches the current list at https://www.iana.org/assignments/rtp-parameters/rtp-parameters.xhtml#rtp-parameters-5 as of 2021-September.