MdeModulePkg/AcpiTableDxe: use pool allocations when possible

MdeModulePkg/AcpiTableDxe: use pool allocations when possible

On AArch64 systems, page based allocations for memory types that are
relevant to the OS are rounded up to 64 KB multiples. This wastes
some space in the ACPI table memory allocator, since it uses page
based allocations in order to be able to place the ACPI tables low
in memory.

Since the latter requirement does not exist on AArch64, switch to pool
allocations for all ACPI tables except the root tables if the active
allocation policy permits them to be anywhere in memory. The root
tables will be handled in a subsequent patch.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>