greybus: svc: make sure to deactivate all interfaces on disconnect

Make sure to deactivate all interfaces when the svc is going away.

This is needed to eventually be able to do controlled teardown of the
unipro network.

Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>