firmware: arm_scmi: Add Powercap protocol enable support

SCMI powercap protocol v3.2 supports disabling the powercap on a zone
by zone basis by providing a zero valued powercap.

Expose new operations to enable/disable powercapping on a per-zone base.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20230531152039.2363181-3-cristian.marussi@arm.com


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