agp/intel: Remove confusion of stolen entries not stolen memory

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/include/drm/intel-gtt.h b/include/drm/intel-gtt.h
index d3c81946..020f8aa 100644
--- a/include/drm/intel-gtt.h
+++ b/include/drm/intel-gtt.h
@@ -2,17 +2,16 @@
 
 #ifndef _DRM_INTEL_GTT_H
 #define	_DRM_INTEL_GTT_H
-struct intel_gtt {
-	/* Number of stolen gtt entries at the beginning. */
-	unsigned int gtt_stolen_entries;
+
+const struct intel_gtt {
+	/* Size of memory reserved for graphics by the BIOS */
+	unsigned int stolen_size;
 	/* Total number of gtt entries. */
 	unsigned int gtt_total_entries;
 	/* Part of the gtt that is mappable by the cpu, for those chips where
 	 * this is not the full gtt. */
 	unsigned int gtt_mappable_entries;
-};
-
-struct intel_gtt *intel_gtt_get(void);
+} *intel_gtt_get(void);
 
 #endif