greybus: control: add bundle-version operation

Add bundle-version operation to fetch the version of the bundle class.

Retrieve the bundle version of all bundles when initialising the
interface in case the control-protocol version is greater than 0.1.

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