Platform/Sgi: prepare SRAT, HMAT table

The primary objective of this patch is to create SRAT, HMAT table at
runtime based on configuration data found by discovering remote CXL Mem
device. In SRAT table, the Localmemory, GICC structure information
remain Static, but only configuration data about Remote memory node is
updated at runtime. In HMAT the latency numbers are not tuned to actual
performance values in current solution. After consolidating all
structure data, SRAT and HMAT tables are installed.

This patch creates and registers notifier event in AcpiTableGenerator
DXE, and the event depends on CXL protocol interface, so that remote
memory node population in SRAT, HMAT tables can be performed after CXL
device discovery and necessary configuration.

While preparing SRAT table, CXL memory information (number of memory
nodes, remote memory size) is fetched from CXL Dxe using CXLprotocol
interfaces. If remote CXL memory is present then from the reserved Host
address space an area equal to remote CXL memory size will be added to
EFI System Memory space. The memory is EfiGcdMemoryTypeSystemMemory and
has Normal memory attributes.

In Single-Chip scenario, one of the primary use case, of having extended
remote memory area and SRAT,HMAT table, is to avail CXL.Memory device as
memory expander.

Signed-off-by: Sayanta Pattanayak <sayanta.pattanayak@arm.com>
Change-Id: I01488ae9cf34b22177ef3d732f674be3e0409f21