[media] DocBook/audio.xml: match section ID's with the reference links

Make sure that both audio.h.xml and audio.xml will match the same names.
This way, it is now possible to identify API spec gaps:

Error: no ID for constraint linkend: AUDIO_CONTINUE.
Error: no ID for constraint linkend: AUDIO_GET_PTS.
Error: no ID for constraint linkend: AUDIO_BILINGUAL_CHANNEL_SELECT.

While here, fix the cut-and-paste description error on AUDIO_SET_KARAOKE.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>