DynamicTablesPkg: AML grammar definition

DynamicTablesPkg: AML grammar definition

ASL is a source language for defining ACPI objects including
writing ACPI control methods. An ASL file is compiled using
an ASL compiler tool to generate ACPI Machine Language (AML).
This AML bytecode is processed by the ACPI AML interpreter
that runs as part of an Operating System (OS).

Both ASL and AML are declarative languages. Although they
are closely related they are different languages.

ASL statements declare objects. Each object has three parts,
two of which can be NULL:
  Object := ObjectType FixedList VariableList

The AML grammar defines corresponding encodings that makes
up the AML byte stream.

This patch introduces the AML grammar definitions used by
AmlLib for encoding/decoding AML byte streams.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Alexei Fedorov <Alexei.Fedorov@arm.com>