drm/i915: warn when a vblank wait times out

This always indicates a bug somewhere.
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -765,7 +765,7 @@ static void g4x_wait_for_vblank(struct drm_device *dev, int pipe)
 	frame = I915_READ(frame_reg);
 
 	if (wait_for(I915_READ_NOTRACE(frame_reg) != frame, 50))
-		DRM_DEBUG_KMS("vblank wait timed out\n");
+		WARN(1, "vblank wait timed out\n");
 }
 
 /**