Control.Power.Mode: Add System Power Mode Interface YAML

Define the system power mode interface. This will allow users
to set the power mode for a system.  The power mode defines
how the processor frequency will be set based on power and
performance.  This is part of the Redfish 2021.1 Schema.

Signed-off-by: Chris Cain <cjcain@us.ibm.com>
Change-Id: Ifd1145b1e0a31c9c71e2377de1cb01fcba5a4188
diff --git a/xyz/openbmc_project/Control/Power/Mode.interface.yaml b/xyz/openbmc_project/Control/Power/Mode.interface.yaml
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+description: >
+    Customer requested system power mode.
+
+properties:
+    - name: PowerMode
+      type: enum[self.PowerMode]
+      description: >
+          This property shall contain the computer system power mode setting.
+          This defines the processor speed based on the priority of power
+          consumption and performance.
+
+enumerations:
+    - name: PowerMode
+      description: >
+        Possible Power Mode settings
+      values:
+        - name: Static
+          description: >
+              This value shall indicate the system performs at a static base
+              speed.
+        - name: PowerSaving
+          description: >
+              This value shall indicate the system performs at reduced speeds
+              to save power. This mode should be used when power saving is the
+              top priority.
+        - name: MaximumPerformance
+          decription: >
+              This value shall indicate the system performs at the highest
+              speeds possible. This mode should be used when performance is
+              the top priority.
+        - name: OEM
+          description: >
+              This value shall indicate the system performs at an OEM-defined
+              power mode.