Bluetooth: Add support to advertise when connected

So far, kernel did not allow to advertise when there was a connection
established. With this patch kernel does allow it if controller
supports it.

If controller supports non-connectable advertising when connected, then
only non-connectable advertising instances will be advertised.

Signed-off-by: Łukasz Rymanowski <lukasz.rymanowski@codecoup.pl>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>