Bluetooth: Return whether a connection is outbound

When an MGMT_EV_DEVICE_CONNECTED event is reported back to the user
space we will set the flags to tell if the established connection is
outbound or not. This is useful for the user space to log better metrics
and error messages.

Reviewed-by: Miao-chen Chou <mcchou@chromium.org>
Reviewed-by: Alain Michaud <alainm@chromium.org>
Signed-off-by: Yu Liu <yudiliu@google.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>