Platform/Sgi: Add rdn2 platform specific acpi tables

The IO topology on the RD-N2 platform is built using the IO
Virtualization block. There are five instances of the IO Virtualization
block on the RD-N2 platform and four of these instances are used to
connect to PCIe root bridge. Add RD-N2 platform specific IORT, MCFG and
SSDT ACPI tables to represent this IO topology.

Signed-off-by: Vivek Gautam <vivek.gautam@arm.com>
Signed-off-by: Vijayenthiran Subramaniam <vijayenthiran.subramaniam@arm.com>
Change-Id: I095114b2bb894b969af0b03aa330e046246f2562