[media] cec-funcs.h: add missing 'reply' for short audio descriptor

The cec_msg_request_short_audio_descriptor function was missing the reply
argument. That's needed if you want the framework to wait for the reply
message.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>