greybus: firmware: Send AP-ready operation

Module's Bootrom needs a way to know (currently), when to start sending
requests to the AP. The version request is sent before connection_init()
routine is called, and if the module sends the request right after
receiving version request, the connection->private field will be NULL.

Fix this TEMPORARILY by sending an AP_READY request.

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