EmbeddedPkg/AcpiLib: Add more helper functions

This adds more helper functions that assist in calculating the checksum,
locating an ACPI table by signature, and updating an AML integer object.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Daniel Schaefer <daniel.schaefer@hpe.com>
Signed-off-by: Nhi Pham <nhi@os.amperecomputing.com>
Acked-by: Leif Lindholm <leif@nuviainc.com>
Reviewed-by: Abner Chang <abner.chang@hpe.com>

EmbeddedPkg/Library/AcpiLib/AcpiLib.inf

@@ -1,6 +1,7 @@
 #/** @file
 #
 #  Copyright (c) 2014, ARM Ltd. All rights reserved.
+#  Copyright (c) 2021, Ampere Computing LLC. All rights reserved.
 #
 #  SPDX-License-Identifier: BSD-2-Clause-Patent
 #
@@ -23,6 +24,8 @@
   EmbeddedPkg/EmbeddedPkg.dec
 
 [LibraryClasses]
+  BaseLib
+  BaseMemoryLib
   DebugLib
   UefiBootServicesTableLib