Platform/Sgi: Add Ssdt and Mcfg tables for RD-N2

RD-N2 platform is updated to have five PCIe segments with 32 buses
under each segments. So add new Ssdt and Mcfg tables specific to RD-N2
platform with five segments each with different ECAM base addresses and
MMIO addresses.

Change-Id: Ice3b54d32cb22561f766b67911da01890b79d5c0
Signed-off-by: Vijayenthiran Subramaniam <vijayenthiran.subramaniam@arm.com>
Signed-off-by: Vivek Gautam <vivek.gautam@arm.com>