greybus: connection: remove disable from destructor

Remove implicit disable of legacy connections from the destructor.

This is a step towards removing the legacy-protocol handling from core.

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