MdePkg/Include/IndustryStandard: Main CXL header

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2611

Introducing the Cxl.h as the main header file to support all versions
of Compute Express Link Specification register definitions.

Signed-off-by: Ashraf Javeed <ashraf.javeed@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>

MdePkg/Include/IndustryStandard/Cxl.h

@@ -0,0 +1,22 @@
+/** @file
+  Support for the latest CXL standard
+
+  The main header to reference all versions of CXL Base specification registers
+  from the MDE
+
+Copyright (c) 2020, Intel Corporation. All rights reserved.<BR>
+SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#ifndef _CXL_MAIN_H_
+#define _CXL_MAIN_H_
+
+#include <IndustryStandard/Cxl11.h>
+//
+// CXL assigned new Vendor ID
+//
+#define CXL_DVSEC_VENDOR_ID                                             0x1E98
+
+#endif
+