drm/virtio: fix memory leak in virtio_gpu_cleanup_object()

Before setting shmem->pages to NULL, kfree() should
be called.
Signed-off-by: NXin He <hexin.op@bytedance.com>
Reviewed-by: NQi Liu <liuqi.16@bytedance.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20200722051851.72662-1-hexin.op@bytedance.comSigned-off-by: NGerd Hoffmann <kraxel@redhat.com>

drivers/gpu/drm/virtio/virtgpu_object.c

@@ -79,6 +79,7 @@ void virtio_gpu_cleanup_object(struct virtio_gpu_object *bo)
 			}
 
 			sg_free_table(shmem->pages);
+			kfree(shmem->pages);
 			shmem->pages = NULL;
 			drm_gem_shmem_unpin(&bo->base.base);
 		}