drm/i915: Remove the broken flush_ring from page-flip

This is already performed with the pipelined flush, so by the time we
schedule the flush in the page-flip, the ring is NULL and we OOPs
instead.
Reported-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_drv.h

@@ -1007,11 +1007,6 @@ int i915_gem_object_put_fence_reg(struct drm_gem_object *obj,
 void i915_gem_retire_requests(struct drm_device *dev);
 void i915_gem_reset_lists(struct drm_device *dev);
 void i915_gem_clflush_object(struct drm_gem_object *obj);
-void i915_gem_flush_ring(struct drm_device *dev,
-			 struct drm_file *file_priv,
-			 struct intel_ring_buffer *ring,
-			 uint32_t invalidate_domains,
-			 uint32_t flush_domains);
 int i915_gem_object_set_domain(struct drm_gem_object *obj,
 			       uint32_t read_domains,
 			       uint32_t write_domain);

drivers/gpu/drm/i915/i915_gem.c

@@ -1924,7 +1924,7 @@ i915_wait_request(struct drm_device *dev, uint32_t seqno,
 	return i915_do_wait_request(dev, seqno, 1, ring);
 }
 
-void
+static void
 i915_gem_flush_ring(struct drm_device *dev,
 		    struct drm_file *file_priv,
 		    struct intel_ring_buffer *ring,

drivers/gpu/drm/i915/intel_display.c

@@ -5028,7 +5028,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 	struct intel_unpin_work *work;
 	unsigned long flags, offset;
 	int pipe = intel_crtc->pipe;
-	u32 was_dirty, pf, pipesrc;
+	u32 pf, pipesrc;
 	int ret;
 
 	work = kzalloc(sizeof *work, GFP_KERNEL);
@@ -5057,7 +5057,6 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 	obj = intel_fb->obj;
 
 	mutex_lock(&dev->struct_mutex);
-	was_dirty = obj->write_domain & I915_GEM_GPU_DOMAINS;
 	ret = intel_pin_and_fence_fb_obj(dev, obj, true);
 	if (ret)
 		goto cleanup_work;
@@ -5076,10 +5075,6 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 	atomic_inc(&obj_priv->pending_flip);
 	work->pending_flip_obj = obj;
 
-	/* Schedule the pipelined flush */
-	if (was_dirty)
-		i915_gem_flush_ring(dev, NULL, obj_priv->ring, 0, was_dirty);
-
 	if (IS_GEN3(dev) || IS_GEN2(dev)) {
 		u32 flip_mask;