greybus: connection: add helper for creating offloaded connection

Add helper for creating offloaded connection.

This can later be extended to support more elaborate resource
management.

Also fix a minor white space issue.

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>