drm/i915,agp/intel: Do not clear stolen entries

We can only utilize the stolen portion of the GTT if we are in sole
charge of the hardware. This is only true if using GEM and KMS,
otherwise VESA continues to access stolen memory.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: Frederic Weisbecker <fweisbec@gmail.com>
Tested-by: Jiri Olsa <jolsa@redhat.com>
Tested-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 5969f46..a0149c6 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -543,8 +543,11 @@
 		/** List of all objects in gtt_space. Used to restore gtt
 		 * mappings on resume */
 		struct list_head gtt_list;
-		/** End of mappable part of GTT */
+
+		/** Usable portion of the GTT for GEM */
+		unsigned long gtt_start;
 		unsigned long gtt_mappable_end;
+		unsigned long gtt_end;
 
 		struct io_mapping *gtt_mapping;
 		int gtt_mtrr;