add support for parsing ac-3 audio descriptor 0x81

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
dr_a0: rename dvbpsi_ExtendedChannelNameeDr to dvbpsi_ExtendedChannelNameDr

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>