schema: ibm: add default power mode props. schema

Add PowerModeProperties schema to define the factory default power mode
properties of a system:
- Power Mode
- Idle Power Saver Parameters

All of these parameters are part of the version 2021.2 Redfish Schema
Supplement under the ComputerSystem 1.16.0 schema:
For details on the values and descriptions, see the PowerMode and
IdlePowerSaver schemas in the Redfish documentation:
https://www.dmtf.org/sites/default/files/standards/documents/DSP0268_2021.2.pdf

These are the factory default values as defined by the system architect.
All of these parameters are system-wide parameters and are used to
define the operation of that system as it relates to power.

These are the values will be used the first time a system is powered on.
They can also be used if the customer wants to restore these settings to
their factory defaults.

Signed-off-by: Chris Cain <cjcain@us.ibm.com>
Change-Id: Ie2f3ca74db0c898c6a4f3beed29eda674dfcf5c6
diff --git a/schemas/global.json b/schemas/global.json
index 164a2ed..f939771 100644
--- a/schemas/global.json
+++ b/schemas/global.json
@@ -9,6 +9,9 @@
             ],
             "oneOf": [
                 {
+                    "$ref": "ibm.json#/definitions/PowerModeProperties"
+                },
+                {
                     "$ref": "ibm.json#/definitions/IBMCompatibleSystem"
                 },
                 {