Platform/Sgi: Add Iort table for RD-N2-Cfg1 platform

Add Iort table specific to RD-N2-Cfg1 platform. RD-N2-Cfg1 has two PCIe
root buses and each of them are connected to an ITS node. The remapping
topology for each PCI RC node to ITS node is shown below:

  0x0000  ---------------   0x60000   ------------
         |  PCIe device  |---------->|     ITS    |
         | (RequesterID) |           | (DeviceID) |
  0xFFFF  ---------------   0x6FFFF   ------------

Signed-off-by: Vijayenthiran Subramaniam <vijayenthiran.subramaniam@arm.com>
Change-Id: Iaac4902ef6396497fba18aef179f997a7192b9c7