Bluetooth: Fix __l2cap_no_conn_pending() usage with all channels

The __l2cap_no_conn_pending() function would previously only return a
meaningful value for connection oriented channels and was therefore not
useful for anything else. As preparation of making the L2CAP code more
generic allow the function to be called for other channel types as well
by returning a meaningful value for them.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>