PowerSupply, Chassis: add powering association

Create association documentation between Chassis and PowerSupply.
For a machine with multiple chassis, it is necessary to indicate which
chassis a PowerSupply is managed by.
One example is that the ChassisID and PowerSupplyID in the Redfish URL
need to match, so we can confirm it through this association.

Signed-off-by: Chicago Duan <duanzhijia01@inspur.com>
Change-Id: I6beb18fd0b621cec6cd4a38606e009cda40f9761
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>

yaml/xyz/openbmc_project/Inventory/Item/Chassis.interface.yaml

@@ -43,3 +43,13 @@ enumerations:
             description: >
                 A logical division or portion of a physical chassis that contains
                 multiple devices or systems that cannot be physically separated.
+
+associations:
+    - name: powered_by
+      description: >
+          Objects that implement Chassis can optionally implement the
+          'powered_by' association to provide a link to one or more
+          power supplies.
+      reverse_name: powering
+      required_endpoint_interfaces:
+          - xyz.openbmc_project.Inventory.Item.PowerSupply

yaml/xyz/openbmc_project/Inventory/Item/PowerSupply.interface.yaml

@@ -1,2 +1,11 @@
 description: >
     Implement to provide PowerSupply attributes.
+
+associations:
+    - name: powering
+      description: >
+          Objects that implement PowerSupply can optionally implement the
+          'powering' association to provide a link back to a Chassis.
+      reverse_name: powered_by
+      required_endpoint_interfaces:
+          - xyz.openbmc_project.Inventory.Item.Chassis