firmware: arm_scmi: Implement is_notify_supported callback in power protocol

Add a preliminary check to verify if the power 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/20240212123233.1230090-5-cristian.marussi@arm.com


Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>