EmbeddedPkg: Add DtPlatformLoaderLib gmock support

Add Google Mock Library for DtPlatformLoaderDtbLib

Signed-off-by: Jeff Brasen <jbrasen@nvidia.com>

EmbeddedPkg/Test/Mock/Include/GoogleTest/Library/MockDtPlatformDtbLoaderLib.h

@@ -0,0 +1,31 @@
+/** @file
+  Google Test mocks for DtPlatformDtbLoaderLib
+
+  Copyright (c) 2023 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+  Copyright (c) 2023, Intel Corporation. All rights reserved.
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#ifndef MOCK_DT_PLATFORM_DTB_LOADER_LIB_H_
+#define MOCK_DT_PLATFORM_DTB_LOADER_LIB_H_
+
+#include <Library/GoogleTestLib.h>
+#include <Library/FunctionMockLib.h>
+extern "C" {
+  #include <Pi/PiMultiPhase.h>
+  #include <Uefi.h>
+  #include <Library/DtPlatformDtbLoaderLib.h>
+}
+
+struct MockDtPlatformDtbLoaderLib {
+  MOCK_INTERFACE_DECLARATION (MockDtPlatformDtbLoaderLib);
+
+  MOCK_FUNCTION_DECLARATION (
+    EFI_STATUS,
+    DtPlatformLoadDtb,
+    (OUT   VOID   **Dtb,
+     OUT   UINTN  *DtbSize)
+    );
+};
+
+#endif