removal of old XboxOneStuff

Source/Engine/Graphics/Graphics.Build.cs

@@ -55,11 +55,11 @@ public class Graphics : EngineModule
             else
                 Log.WarningOnce("Building for Windows without DirectX 12 rendering backend (Windows 10 SDK is required)", ref _logMissingWindowsSDK);
             break;
-        case TargetPlatform.XboxOne:
         case TargetPlatform.UWP:
             options.PrivateDependencies.Add("GraphicsDeviceDX11");
             break;
-        case TargetPlatform.XboxScarlett:
+            case TargetPlatform.XboxOne:
+            case TargetPlatform.XboxScarlett:
             options.PrivateDependencies.Add("GraphicsDeviceDX12");
             break;
         case TargetPlatform.Linux:

Source/Engine/Graphics/Graphics.cpp

@@ -155,6 +155,14 @@ bool GraphicsService::Init()
             device = CreateGPUDevicePS4();
 #endif
 
+#elif PLATFORM_XBOX_ONE
+
+        // Xbox One
+#if GRAPHICS_API_DIRECTX12
+        if (!device)
+            device = CreateGPUDeviceDX12();
+#endif
+
 #elif PLATFORM_XBOX_SCARLETT
 
         // Xbox Scarlett