drm/i915: Discard the unused obj->last_fenced_ring

As we now never pipeline a fence update, obj->last_fenced_ring is always
the same as the obj->ring whenever obj->last_fenced_seqno is active, so
remove it.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 6a504f9..69e1539 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -930,13 +930,12 @@
 	 */
 	uint32_t gtt_offset;
 
-	/** Breadcrumb of last rendering to the buffer. */
-	uint32_t last_rendering_seqno;
 	struct intel_ring_buffer *ring;
 
+	/** Breadcrumb of last rendering to the buffer. */
+	uint32_t last_rendering_seqno;
 	/** Breadcrumb of last fenced GPU access to the buffer. */
 	uint32_t last_fenced_seqno;
-	struct intel_ring_buffer *last_fenced_ring;
 
 	/** Current tiling stride for the object, if it's tiled. */
 	uint32_t stride;