[Bluetooth] Allow security for outgoing L2CAP connections

When requested the L2CAP layer will now enforce authentication and
encryption on outgoing connections. The usefulness of this feature
is kinda limited since it will not allow proper connection ownership
tracking until the authentication procedure has been finished. This
is a limitation of Bluetooth 2.0 and before and can only be fixed by
using Simple Pairing.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>