MdePkg: Add AML FieldList OpCode definitions

The ACPI specification, version 6.3, January 2019,
defines the Named Objects Encoding for FieldElements
in section '20.2.5.2 Named Objects Encoding'.
FieldElements can be one of the following:
NamedField | ReservedField | AccessField |
ExtendedAccessField | ConnectField

Some of these keywords are starting with an opcode,
allowing to identify their type.
E.g.: ReservedField := 0x00 PkgLength

This patch adds these FieldElement opcodes definitions to
the list of AML Opcode definitions.

Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Zhiguang Liu <zhiguang.liu@intel.com>
Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>

MdePkg/Include/IndustryStandard/AcpiAml.h

@@ -168,4 +168,12 @@
 #define AML_EXT_BANK_FIELD_OP        0x87
 #define AML_EXT_DATA_REGION_OP       0x88
 
+//
+// FieldElement OpCode
+//
+#define AML_FIELD_RESERVED_OP        0x00
+#define AML_FIELD_ACCESS_OP          0x01
+#define AML_FIELD_CONNECTION_OP      0x02
+#define AML_FIELD_EXT_ACCESS_OP      0x03
+
 #endif