drm/i915: Remove gtt_bound from drm_i915_gem_object

This wasn't even used as far as I could tell and will only confuse
people (like me).
Signed-off-by: Ben Gamari <bgamari.foss@gmail.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/i915_drv.h

@@ -489,9 +489,6 @@ struct drm_i915_gem_object {
 	 */
 	int fence_reg;
 
-	/** Boolean whether this object has a valid gtt offset. */
-	int gtt_bound;
-
 	/** How many users have pinned this object in GTT space */
 	int pin_count;