greybus: connection: call gb_svc_connection_create() from gb_connection_init()

There are two operations which very much work together:
- AP asks the SVC to create a connection between a cport of AP and a
  cport of module.
- AP tells the module that the connection is created.

Its better (logically) to do these two operations together and so call
gb_svc_connection_create() from gb_connection_init() instead. Also check
its return value properly.

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>