greybus: bundle: separate bundle creation and registration

Separate bundle creation and registration.

Note that the bundle connections still needs to be initialised post
registration as protocol drivers create child devices to the bundle.

This will ultimately allow connection structures to be created while
parsing manifests, but the connections to not be enabled until a driver
is bound.

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>