drm/xe/mocs: Drop HAS_RENDER_L3CC flag

The HAS_RENDER_L3CC is set unconditionally so there's no need to keep it
as a dedicated flag.  For error checking purposes, we can just make sure
the 'table' field is initialized properly.

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Suggested-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>