firmware: arm_scmi: Implement is_notify_supported callback in powercap protocol

firmware: arm_scmi: Implement is_notify_supported callback in powercap protocol

Add a preliminary check to verify if the powercap protocol related notify
enable commands are supported at all by the SCMI platform, and then
provide the callback needed to allow the core SCMI notification
subsytem to do a fine-grain check if a specific resource domain
supports notifications.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20240212123233.1230090-10-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>