of-graph: export symbol of_phandle_iterator_init/next

of_for_each_phandle() uses of_phandle_iterator_init/next
but it isn't exported. So kernel module complile will say

ERROR: "of_phandle_iterator_init" [xxx.ko] undefined!
ERROR: "of_phandle_iterator_next" [xxx.ko] undefined!

This patch solved this issue
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/of/base.c

@@ -1601,6 +1601,7 @@ int of_phandle_iterator_init(struct of_phandle_iterator *it,
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(of_phandle_iterator_init);
 
 int of_phandle_iterator_next(struct of_phandle_iterator *it)
 {
@@ -1670,6 +1671,7 @@ int of_phandle_iterator_next(struct of_phandle_iterator *it)
 
 	return -EINVAL;
 }
+EXPORT_SYMBOL_GPL(of_phandle_iterator_next);
 
 int of_phandle_iterator_args(struct of_phandle_iterator *it,
 			     uint32_t *args,