A flag is added to let the transport signal the core that its handling of
synchronous command messages implies that, after .send_message has returned
successfully, the requested command can be assumed to be fully and
completely executed on SCMI platform side so that any possible response
value is already immediately available to be retrieved by a .fetch_reponse:
in other words the polling phase can be skipped in such a case and the
response values accessed straight away.
Note that all of the above applies only when polling mode of operation was
selected by the core: if instead a completion IRQ was found to be available
the normal response processing path based on completions will still be
followed.