drm/xe: Enable W=1 warnings by default

Like done in commit 2250c7ea

 ("drm/i915: enable W=1 warnings by default")
for i915, enable W=1 warnings by default in xe.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>