MdePkg: Add CEDT structure

CXL Early Discovery Table (CEDT) enables OSes to locate CXL Host Bridges
and location of Host Bridge Registers early during boot and configure
Host Bridge Decoders according to ACPI information.

This patch adds CEDT structures of type CXL Host Bridge Structure (CHBS)
and CXL Fixed Memory Window Structure (CFMWS) according to CXL
specification, Revision 3.0, Version 0.7.

Signed-off-by: Sayanta Pattanayak <sayanta.pattanayak@arm.com>
Change-Id: I8e2141594c4469ebe712b7717a5268f983bd5d44