Bluetooth: sco: prevent information leak in sco_conn_defer_accept()

Smatch complains that some of these struct members are not initialized
leading to a stack information disclosure:

    net/bluetooth/sco.c:778 sco_conn_defer_accept() warn:
    check that 'cp.retrans_effort' doesn't leak information

This seems like a valid warning.  I've added a default case to fix
this issue.

Fixes: 2f69a82a ("Bluetooth: Use voice setting in deferred SCO connection request")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>