Add PSU FRU to Redfish

Add PSU FRU to Redfish chassis or baseboard.

Tested:
Check redfish
https://BMC_IP/redfish/v1/Chassis/WC_Baseboard/Power
Page will show:
"PowerSupplies": [
    {
        "@odata.id": "/redfish/v1/Chassis/WC_Baseboard/Power#/PowerSupplies/0",
        "Manufacturer": "SOLUM CO., LTD.                  ",
        "MemberId": "SOLUM_CO_IS162F22_PSU1",
        "Model": "IS162F22",
        "Name": "SOLUM CO IS162F22 PSU1",
        "PartNumber": "G36234-014",
        "PowerInputWatts": 0.0,
        "PowerOutputWatts": 0.0,
        "SerialNumber": "PSSF162202ACNS1622A4BJCB0259",
        "Status": {
            "Health": "OK",
            "State": "Enabled"
        }
    },
    {
        "@odata.id": "/redfish/v1/Chassis/WC_Baseboard/Power#/PowerSupplies/1",
        "Manufacturer": "SOLUM CO., LTD.                  ",
        "MemberId": "SOLUM_CO_IS162F22_PSU2",
        "Model": "IS162F22",
        "Name": "SOLUM CO IS162F22 PSU2",
        "PartNumber": "G36234-013",
        "PowerInputWatts": 152.75,
        "PowerOutputWatts": 135.75,
        "SerialNumber": "PSSF162202ACNS1622A4BJ890333",
        "Status": {
            "Health": "OK",
            "State": "Enabled"
        }
    }
],

Signed-off-by: Cheng C Yang <cheng.c.yang@linux.intel.com>
Change-Id: I1d104b5a3090cdaa9cea22529150569ebfc24730
diff --git a/src/PSUSensor.cpp b/src/PSUSensor.cpp
index 58dee54..015a367 100644
--- a/src/PSUSensor.cpp
+++ b/src/PSUSensor.cpp
@@ -57,10 +57,12 @@
         thresholdInterfaceCritical = objectServer.add_interface(
             dbusPath, "xyz.openbmc_project.Sensor.Threshold.Critical");
     }
+    setInitialProperties(conn);
+
     association =
         objectServer.add_interface(dbusPath, "org.openbmc.Associations");
 
-    setInitialProperties(conn);
+    createInventoryAssoc(conn, association, configurationPath);
     setupRead();
 }