drm/xe: Select DRM_CLIENT_SELECTION

The Kconfig token DRM_CLIENT_SELECTION will make DRM clients
available to drivers. Select it from xe.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241014085740.582287-3-tzimmermann@suse.de