drm/xe: Use the filelist from drm for ccs_mode change

drm/xe: Use the filelist from drm for ccs_mode change

Drop the exclusive client count tracking and use the filelist from the
drm to track the active clients. This also ensures the clients created
internally by the driver won't block changing the ccs mode.

Fixes: ce8c161cbad4 ("drm/xe: Add ref counting for xe_file")
Signed-off-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241008073628.377433-3-balasubramani.vivekanandan@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>