greybus: interface: Get manifest using Control protocol

Control protocol is ready to be used for fetching manifest. Lets do it.

This changes few things:
- Creates/initializes bundle/connection for control protocol initially
  and skips doing the same later.
- Manifest is parsed at link-up now, instead of hotplug which was the
  case earlier. This is because we need device_id (provided during
  link-up) for registering bundle.
- Manifest is fetched using control protocol.

So the sequence of events is:

Event                 Previously       Now
-----                 ----------       ---
Interface Hotplug     create intf      create intf
                      parse mfst

Interface Link Up     init bundles     create control conn
                                       get mfst size
                                       get mfst
                                       parse mfst
                                       init bundles

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