greybus: manifest: Allow bundles/connections list to be non-empty at manifest parsing

A connection and a bundle will be created for interfaces at the very
beginning for control protocol's functioning. And so the list of bundles
and connections for a interface will be non-empty by the time manifest
is parsed.

Currently we are firing a WARN when these lists are found to be
non-empty. Lets fix that to contain single bundle and connection for
control protocol.

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