firmware: arm_scmi: Harden perf domain info access

Harden internal accesses to domain info in the SCMI perf protocol.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20230717161246.1761777-2-cristian.marussi@arm.com


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