cdx: Create symbol namespaces for cdx subsystem

Create CDX_BUS and CDX_BUS_CONTROLLER symbol namespace for cdx bus
subsystem. CDX controller modules are required to import symbols from
CDX_BUS_CONTROLLER namespace and other than controller modules to
import from CDX_BUS namespace.

Signed-off-by: Abhijit Gangurde <abhijit.gangurde@amd.com>
Link: https://lore.kernel.org/r/20231017160505.10640-4-abhijit.gangurde@amd.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>