firmware: arm_scmi: Add SCMI v3.1 perf power-cost in microwatts

Add SCMI v3.1 internal support for parsing message attributes reporting
the capability of a performance domain to report power-cost in microwatts.

Link: https://lore.kernel.org/r/20220330150551.2573938-22-cristian.marussi@arm.com


Cc: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>