drm/tegra: fb: Do not destroy framebuffer

Drop a reference instead of directly calling the framebuffer .destroy()
callback at fbdev free time. This is necessary to make sure the object
isn't destroyed if anyone else still has a reference.
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NThierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/fb.c

@@ -360,7 +360,7 @@ static void tegra_fbdev_exit(struct tegra_fbdev *fbdev)
 
 	if (fbdev->fb) {
 		drm_framebuffer_unregister_private(&fbdev->fb->base);
-		tegra_fb_destroy(&fbdev->fb->base);
+		drm_framebuffer_remove(&fbdev->fb->base);
 	}
 
 	drm_fb_helper_fini(&fbdev->base);