Platform/Sgi: Add ACPI tables for RD-N2-Cfg2 platform

Add Madt, Dsdt, Iort, Mcfg, Srat and Ssdt ACPI tables that are specific
for RD-N2-Cfg2 platform. Reuse the rest of the shared ACPI tables in
SgiPkg.

Signed-off-by: Aditya Angadi <aditya.angadi@arm.com>
Change-Id: I33677ce8f3240637c5a9ef012c0d730cc6f5540c