Adjust parameter name of FirmwareInventoryId

redfish URL "/redfish/v1/UpdateService/FirmwareInventory/
{SoftwareInventoryId}" had parameter called "Members@odata.count".

This parameter name is not appropriate because it retrieves data, count
of Related Item, from "RelatedItem" parameter, so its name has to be
"RelatedItem@odata.count".

Implement:
  Updated name of JSON parameter, also updated code variable name.

Tested: Validator passes

- Keep primary data and other parameter deleted from JSON data
Old JSON data:
  {
    "@odata.id": "/redfish/v1/UpdateService/FirmwareInventory/
    {SoftwareInventoryId},
    "@odata.type": "#SoftwareInventory.v1_1_0.SoftwareInventory",
    "Description": "BMC image",
    "Members@odata.count": 1,
    "Name": "Software Inventory",
    "RelatedItem": [{
      "@odata.id": "/redfish/v1/Managers/bmc"
    }],
  }
new JSON data:
  {
    "@odata.id": "/redfish/v1/UpdateService/FirmwareInventory/
    {SoftwareInventoryId},
    "@odata.type": "#SoftwareInventory.v1_1_0.SoftwareInventory",
    "Description": "BMC image",
    "RelatedItem@odata.count": 1,
    "Name": "Software Inventory",
    "RelatedItem": [{
      "@odata.id": "/redfish/v1/Managers/bmc"
    }],
  }

Signed-off-by: Abhishek Patel <Abhishek.Patel@ibm.com>
Change-Id: I12c123fc78872890efe2949d2a3a55f882cdd09b