Bluetooth: A2MP: Process A2MP Get AMP Assoc Request

Example trace when receiving AMP Assoc Request with wrong AMP id.
...
> ACL data: handle 11 flags 0x02 dlen 13
    A2MP: Get AMP Assoc req: id 238
< ACL data: handle 11 flags 0x00 dlen 14
    A2MP: Get AMP Assoc rsp: id 238 status (1) Invalid Controller ID
      assoc data:
...

Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>