DynamicTablesPkg: Use AML_NAME_SEG_SIZE define

Use the newly introduced defined value in:
MdePkg/Include/IndustryStandard/AcpiAml.h

Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>

DynamicTablesPkg/Library/Common/AmlLib/AmlDefines.h

@@ -1,7 +1,7 @@
 /** @file
   AML Defines.
 
-  Copyright (c) 2020, Arm Limited. All rights reserved.<BR>
+  Copyright (c) 2020 - 2021, Arm Limited. All rights reserved.<BR>
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 **/
@@ -138,13 +138,6 @@ typedef enum EAmlParseIndex {
 */
 #define AML_FIELD_NAMED_OP            0x04
 
-/** Size of a NameSeg.
-    Cf. ACPI 6.3 specification, s20.2.
-
-  @ingroup TreeStructures
-*/
- #define AML_NAME_SEG_SIZE            4U
-
 /** AML object types.
 
   The ACPI specification defines several object types. They are listed