Bluetooth: audio: Reject QoS if CIS is already is use in this direction

As per ASCS_v1.0
If a client requests a Config QoS operation for an ASE that would
result in more than one (Sink/Source) ASE having identical CIG_ID
and CIS_ID parameter values for that client, the server shall not
accept the Config QoS operation for that ASE.
The server shall send a notification of the ASE Control Point
characteristic to the client, the server shall set the Response_Code
value for that ASE to 0x09 (Invalid Parameter Value), and the server
shall set the Reason value for that ASE to 0x0A
(Invalid_ASE_CIS_Mapping).

Fixes: ASCS/SR/SPE/BI-{15,16}-C
Signed-off-by: Mariusz Skamra <mariusz.skamra@codecoup.pl>