drm/i915: Mark the kernel as tainted if we fail the preproduction check

Preproduction sdv are not supported beyond the release of production
hardware, and continued use is ill-advised. Mark the kernel as tainted
to reinforce the error.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: "Zanoni, Paulo R" <paulo.r.zanoni@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170130104458.2653-2-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

drivers/gpu/drm/i915/i915_drv.c

@@ -784,9 +784,11 @@ static void intel_detect_preproduction_hw(struct drm_i915_private *dev_priv)
 	pre |= IS_HSW_EARLY_SDV(dev_priv);
 	pre |= IS_SKL_REVID(dev_priv, 0, SKL_REVID_F0);
 
-	if (pre)
+	if (pre) {
 		DRM_ERROR("This is a pre-production stepping. "
 			  "It may not be fully functional.\n");
+		add_taint(TAINT_MACHINE_CHECK, LOCKDEP_STILL_OK);
+	}
 }
 
 /**