greybus: connection: send [dis]connected events over control CPort

The AP needs to send connected and disconnection events to all
interfaces, before a CPort (other than control CPort) can be used.

For now do it which we initialize the connection, but it should be moved
to operations code later.

Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>