Platform/Sgi: add CXL driver support

CxlDxe discovers CXL capable device with memory expander capability
and reads out memory range details. Platform drivers fetch the remote
memory details and include as part of system memory through ACPI
tables.

Signed-off-by: Sayanta Pattanayak <sayanta.pattanayak@arm.com>
Change-Id: I65e39c33dc642acf36a0f7e9375aad3b860749bc