remoteproc: sysmon: Expose the shutdown result

remoteproc: sysmon: Expose the shutdown result

A graceful shutdown of the Qualcomm remote processors where
traditionally performed by invoking a shared memory state signal and
waiting for the associated ack.

This was later superseded by the "sysmon" mechanism, where some form of
shared memory bus is used to send a "graceful shutdown request" message
and one of more signals comes back to indicate its success.

But when this newer mechanism is in effect the firmware is shut down by
the time the older mechanism, implemented in the remoteproc drivers,
attempts to perform a graceful shutdown - and as such it will never
receive an ack back.

This patch therefor track the success of the latest shutdown attempt in
sysmon and exposes a new function in the API that the remoteproc driver
can use to query the success and the necessity of invoking the older
mechanism.

Tested-by: Steev Klimaszewski <steev@kali.org>
Reviewed-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>
Link: https://lore.kernel.org/r/20201122054135.802935-3-bjorn.andersson@linaro.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>