Bluetooth: Fix L2CAP error return used for failed channel lookups

The EFAULT error should only be used for memory address related errors
and ENOENT might be needed for other purposes than invalid CID errors.
This patch fixes the l2cap_config_req, l2cap_connect_create_rsp and
l2cap_create_channel_req handlers to use the unique EBADSLT error to
indicate failed lookups on a given CID.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>