Add PowerSupplyAttributes interface

Create a PowerSupply interface to host characteristics for an
individual power supply and add the Derating Factor as a property.
The derating factor is intended as a read-only value.

Tested: Compiled the changes and verified the generated code.

Change-Id: I5f8cdc19239a9a17b0a4ad8383c679b530f1a6b5
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/xyz/openbmc_project/Control/PowerSupplyAttributes.interface.yaml b/xyz/openbmc_project/Control/PowerSupplyAttributes.interface.yaml
new file mode 100644
index 0000000..1e8f1b3
--- /dev/null
+++ b/xyz/openbmc_project/Control/PowerSupplyAttributes.interface.yaml
@@ -0,0 +1,10 @@
+description: >
+    An interface to set control characteristics for an individual power supply.
+properties:
+    - name: DeratingFactor
+      type: uint32
+      flags:
+        - const
+      description: >
+          The power supply derating factor, which is the percentage to multiply
+          the input power by to get the output power.