Platform/Sgi: add remote memory descriptor

8GB address region starting at 0x3FE00000000 is reserved for
extended Remote Memory use. Resource descriptor for remote memory
region is added.

One of the use case, for extended remote memory region, is using
it as CXL.Mem region.

Also marked Local memory block count, for creating SRAT tables in subsequent
patch.

Signed-off-by: Sayanta Pattanayak <sayanta.pattanayak@arm.com>
Change-Id: I8c16b71fcece70f5720203c4c0a0b5f7e51a41ca