drm/i915: Simplify i915_gem_obj_is_pinned() test for set-tiling

Since the removal of the user pin_ioctl, the only means for pinning an
object is either through binding to the scanout or during execbuf
reservation. As the later prevents a call to set-tiling, we need only
check if the obj is pinned into the display plane to see if we need
reject the set-tiling ioctl.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_tiling.c

@@ -336,7 +336,7 @@ i915_gem_set_tiling(struct drm_device *dev, void *data,
 	}
 
 	mutex_lock(&dev->struct_mutex);
-	if (i915_gem_obj_is_pinned(obj) || obj->framebuffer_references) {
+	if (obj->pin_display || obj->framebuffer_references) {
 		ret = -EBUSY;
 		goto err;
 	}