Add support for LocationCode

LocationCode is needed to populate ServiceLabel by BMCWeb for Redfish
resource associated with eStorage.
LocationCode is derived from config object exported by Entity Manager
in the the following interface:
    "xyz.openbmc_project.Configuration.EmmcDevice

To surface LocationCode, the "Exposes" entry in board's Entity Manager
config can add "LocationCode" property as follows:
{
    "Name": "example_emmc",
    "Type": "EmmcDevice",
    "LocationCode": "U1000"
}

Here the LocationCode is the silk screen label.

Tested:

busctl introspect xyz.openbmc_project.eStoraged \
/xyz/openbmc_project/inventory/storage/mmcblk0  \
xyz.openbmc_project.Inventory.Decorator.LocationCode

NAME                TYPE      SIGNATURE RESULT/VALUE FLAGS
.LocationCode    property  s         "U1000"      emits-change

wget -qO- localhost:80/redfish/v1/Chassis/DCSCM/Drives/mmcblk0
{
    "@odata.id": "/redfish/v1/Chassis/DCSCM/Drives/mmcblk0",
    "@odata.type": "#Drive.v1_7_0.Drive",
    "Id": "mmcblk0",
    "Links": {
    "Chassis": {
        "@odata.id": "/redfish/v1/Chassis/DCSCM"
    }
    },
    "Name": "mmcblk0",
    "PhysicalLocation": {
    "PartLocation": {
        "LocationType": "Embedded",
        "ServiceLabel": "U1000"
    },
    "PartLocationContext": "DC_SCM"
    },
    "PredictedMediaLifeLeftPercent": 100,
    "Status": {
    "State": "Enabled"
    }
}

Change-Id: Ibf53ede5ee65787f9cef53d4bad4cb8fccba3606
Signed-off-by: Rahul Kapoor <rahulkpr@google.com>
diff --git a/include/util.hpp b/include/util.hpp
index a6af6ed..ff38cdd 100644
--- a/include/util.hpp
+++ b/include/util.hpp
@@ -52,7 +52,8 @@
  */
 bool findDevice(const StorageData& data, const std::filesystem::path& searchDir,
                 std::filesystem::path& deviceFile,
-                std::filesystem::path& sysfsDir, std::string& luksName);
+                std::filesystem::path& sysfsDir, std::string& luksName,
+                std::string& locationCode);
 
 } // namespace util