Add State information for FabricAdapter

This commit is to add state information according to the Redfish
FabricAdapter schema. If the `xyz.openbmc_project.Inventory.Item`
interface does not exist, the state information property is not
displayed.
ref: http://redfish.dmtf.org/schemas/v1/FabricAdapter.v1_4_0.json

Tested: Validator passes #
```
curl -k  https://$bmc:/redfish/v1/Systems/system/FabricAdapters/disk_backplane0
{
  "@odata.id": "/redfish/v1/Systems/system/FabricAdapters/disk_backplane0",
  "@odata.type": "#FabricAdapter.v1_4_0.FabricAdapter",
  "Id": "disk_backplane0",
  "Location": {
    "PartLocation": {
      "ServiceLabel": "U78DA.ND0.WZS0042-P1"
    }
  },
  "Model": "6B89",
  "Name": "Fabric Adapter",
  "PartNumber": "02WG682",
  "SerialNumber": "YA31UF09P002",
  "SparePartNumber": "02WG681",
  "Status": {
    "State": "Enabled"
  }
}
```

Change-Id: I1e541910d8d3d69b21594ee05e972517d8b8c12d
Signed-off-by: Lakshmi Yadlapati <lakshmiy@us.ibm.com>
diff --git a/redfish-core/lib/fabric_adapters.hpp b/redfish-core/lib/fabric_adapters.hpp
index f6099e6..ba52e67 100644
--- a/redfish-core/lib/fabric_adapters.hpp
+++ b/redfish-core/lib/fabric_adapters.hpp
@@ -118,6 +118,32 @@
         });
 }
 
+inline void
+    getFabricAdapterState(const std::shared_ptr<bmcweb::AsyncResp>& aResp,
+                          const std::string& serviceName,
+                          const std::string& fabricAdapterPath)
+{
+    sdbusplus::asio::getProperty<bool>(
+        *crow::connections::systemBus, serviceName, fabricAdapterPath,
+        "xyz.openbmc_project.Inventory.Item", "Present",
+        [aResp](const boost::system::error_code ec, const bool present) {
+        if (ec)
+        {
+            if (ec.value() != EBADR)
+            {
+                BMCWEB_LOG_ERROR << "DBUS response error for State";
+                messages::internalError(aResp->res);
+            }
+            return;
+        }
+
+        if (!present)
+        {
+            aResp->res.jsonValue["Status"]["State"] = "Absent";
+        }
+        });
+}
+
 inline void doAdapterGet(const std::shared_ptr<bmcweb::AsyncResp>& aResp,
                          const std::string& systemName,
                          const std::string& adapterId,
@@ -133,8 +159,11 @@
     aResp->res.jsonValue["@odata.id"] = crow::utility::urlFromPieces(
         "redfish", "v1", "Systems", systemName, "FabricAdapters", adapterId);
 
+    aResp->res.jsonValue["Status"]["State"] = "Enabled";
+
     getFabricAdapterLocation(aResp, serviceName, fabricAdapterPath);
     getFabricAdapterAsset(aResp, serviceName, fabricAdapterPath);
+    getFabricAdapterState(aResp, serviceName, fabricAdapterPath);
 }
 
 inline bool checkFabricAdapterId(const std::string& adapterPath,