firmware: arm_scmi: Make notifications aware of protocols users

Account for any active registered notifier against the proper related
protocol, do not consider pending event handlers, only active handlers
will concur to protocol usage accounting.

Link: https://lore.kernel.org/r/20210316124903.35011-5-cristian.marussi@arm.com


Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>