drm/exynos: remove exynos_plane_destroy()

The .destroy() callback for exynos can be replaced by drm_plane_cleanup().
The only extra operation on exynos_plane_destroy() was a call to
exynos_plane_disable() but the plane is already disabled by a earlier call
to drm_framebuffer_remove().
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_plane.c

@@ -178,16 +178,10 @@ static int exynos_disable_plane(struct drm_plane *plane)
 	return 0;
 }
 
-static void exynos_plane_destroy(struct drm_plane *plane)
-{
-	exynos_disable_plane(plane);
-	drm_plane_cleanup(plane);
-}
-
 static struct drm_plane_funcs exynos_plane_funcs = {
 	.update_plane	= exynos_update_plane,
 	.disable_plane	= exynos_disable_plane,
-	.destroy	= exynos_plane_destroy,
+	.destroy	= drm_plane_cleanup,
 };
 
 static void exynos_plane_attach_zpos_property(struct drm_plane *plane,