firmware: arm_scmi: Add SCMI v3.1 powercap protocol basic support

Add support for SCMI v3.1 powercap protocol, with the exception of powercap
fast channels, exposing all the new related powercap protocol operations as
usual in include/linux/scmi_protocol.h.

Link: https://lore.kernel.org/r/20220704102241.2988447-3-cristian.marussi@arm.com


Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>