greybus: connection: destroy svc connection on connection exit or errors

While initializing a connection, the AP requests the SVC to create a
connection between a cport on AP and a cport on the Module.

The opposite of that is missing, when connection is destroyed or if
errors occur after creating the connection. Fix it.

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